A Guide for Reducing Speeding-Related Crashes

SECTION V — Description of Strategies

Objectives

The main goal of this guide is the reduction of fatal and severe injury traffic crashes in which speeding or inappropriate speed is a factor. As is the case with most of the guidance in the AASHTO Strategic Highway Safety Plan, effectively addressing these types of collisions involves an interdisciplinary approach; a combination of education, enforcement and engineering measures will often be needed to obtain measurable improvements in safety.

Speeding-related fatalities can occur when drivers are traveling at speeds clearly in excess of the appropriate speed. Fatalities can also result when the selected speed is legal, yet local conditions warrant a lower speed. This guide suggests several objectives for addressing the problem of speeding and inappropriate speed choice.

Specific objectives include improvements in procedures for setting speed limits, driver education programs, speed enforcement programs and engineering features of the roadway environment. Exhibit V-1 lists the objectives and the related strategies for severe crashes that involve speeding or inappropriate speeds.

• Set appropriate speed limits—Setting speed limits to reflect the surrounding context of the roadway and that meet with driver expectations can help improve driver respect for speed limits. Speed limits that appear inconsistent may be ignored by the majority of drivers and this may contribute to lack of respect for speed limit and other traffic laws.
• Heighten driver awareness of speeding-related safety issues—Informing drivers of the risks—both to themselves and to other road users—associated with speeding is intended to encourage drivers to obey speed limits and drive at speeds safe for the roadway environment.
• Improve the effectiveness of speed enforcement efforts—Many crashes are caused or aggravated by drivers' noncompliance with traffic control devices or traffic laws. Effectiveness of enforcement can be increased if drivers perceive there is a significant chance they may be cited for speeding and may be given a hefty fine. Visible conventional or automated enforcement programs, increased fines for repeat offenders, and upholding of citations and levying of fines by courts can increase drivers' perceptions of the enforcement-related risks of speeding.
• Communicate appropriate speeds through use of traffic control devices—Information on appropriate speeds, including permanent speed limits, variable speed limits, and warning speeds, needs to be conveyed clearly to drivers and at appropriate locations. Pavement markings can be used to encourage drivers to proceed at appropriate speeds without actually posting the speed limit. Even though drivers have the responsibility to drive at a safe speed, they need to be able to receive cues from the roadway environment as to what that safe speed is.
• Ensure that roadway design and traffic control elements support appropriate and safe speeds—Geometric design features of roadway sections and intersections, and operation of traffic signals, need to reflect the speeds expected of drivers. For example, roadway designs sensitive to the context in which they will be located can encourage appropriate speed choices by drivers. Geometric elements which affect operating speeds, such as horizontal and vertical curves, can be designed in combinations to encourage appropriate speeds. Intersection types and designs should be appropriate for the context of the roadway. Providing a proper signal co-ordination through intersections along a corridor can create uniform speeds and reduce the need for drivers to stop at the intersections.

Ultimately, the goal toward which the objectives and strategies are directed is to improve safety for all road users by reducing the incidence of speeding and inappropriately high speeds. The strategies discussed in this section combine the elements of education, enforcement, and engineering. Strategies are suggested recognizing that, with few exceptions, programs that depend on only one of these elements are usually not as successful as those which incorporate a range of elements. Some strategies are aimed at general cultural and behavioral attributes of the driving public, while others are targeted at specific high-risk locations or portions of the population. The strategies listed in Exhibit V-1, which are categorized according to the objectives discussed above, are discussed in detail in this section. The order in which the strategies are listed does not imply a priority with which they should be considered.

Most of the strategies are relatively low-cost, short-term treatments for reducing speedingrelated fatalities, consistent with the focus of the entire AASHTO Strategic Highway Safety Plan (SHSP). For each of these, a detailed discussion of the attributes, effectiveness, and other key factors describing the strategy is presented below. Several higher-cost, longerterm strategies which have been proven effective in reducing speeding are also presented in this section, but in less detail. While application of these is outside the implementation framework envisioned by the SHSP, their inclusion in this guide serves to complete the picture of proven, tried, and experimental strategies for reducing speeding-related fatalities. In addition, strategies that have been discussed in other guides in this series, such as some of those related to intersection improvements, are discussed in less detail in this guide, and the reader is encouraged to review the other pertinent volumes.

EXHIBIT V-1
Objectives and Strategies for Addressing Speeding-Related Fatalities

Types of Strategies

The strategies in this guide were identified from a number of sources, including recent literature, contact with state and local agencies throughout the United States, and federal programs. Some of the strategies are widely used, while a few have been subjected to only a limited number of trial applications to date. Some have been subjected to welldesigned evaluations to prove their effectiveness. On the other hand, it was found that many strategies, including some that are widely used, have not been thoroughly evaluated.

The implication of the widely varying experience with these strategies, as well as the range of knowledge about their effectiveness, is that the reader should be prepared to exercise caution in many cases, before adopting a particular strategy for implementation. To help the reader, the strategies have been classified into three types, each identified by letter symbol throughout the guide:

• Proven (P)—Those strategies that have been used in one or more locations and for which properly designed evaluations have been conducted which show them to be effective. These strategies may be employed with a good degree of confidence, but with the understanding that any application can lead to results that vary significantly from those found in previous experience. The attributes of the strategies that are provided will help the users make judgments about which may be the most appropriate for their particular situation(s).
• Tried (T)—Those strategies that have been implemented in a number of locations, and may even be accepted as standards or standard approaches, but for which there have not been found valid evaluations. These strategies, while in frequent or even general use, should be applied with caution, carefully considering the attributes cited in the guide, and relating them to the specific conditions for which they are being considered. Implementation can proceed with some degree of assurance that there is not likely to be a negative impact on safety, and very likely to be a positive one. It is intended that as implementation of these strategies continues under the AASHTO Strategic Highway Safety Plan initiative, appropriate evaluations will be conducted. As more reliable effectiveness information is accumulated to provide better estimating power for the user, any given strategy labeled "tried" can be upgraded to a "proven" one.
• Experimental (E)—Those strategies representing ideas that have been suggested, with at least one agency considering them sufficiently promising to try them as an experiment in at least one location. These strategies should be considered only after the others have been determined not to be appropriate or feasible. Even where they are considered, their implementation should initially occur using a controlled and limited pilot study that includes a properly designed evaluation component. Only after careful testing and evaluations show the strategy to be effective should broader implementation be considered. It is intended that as the experiences of such pilot tests are accumulated from various state and local agencies, the aggregate experience can be used to further detail the attributes of this type of strategy, so that it can be upgraded to a "proven" one or be identified as being ineffective and not worthy of further consideration.

Related Strategies for Creating a Truly Comprehensive Approach

The strategies listed in Exhibit V-1 and described in detail in the remainder of this section are either considered unique to addressing speeding and inappropriate speeds roadways, or are discussed in terms of their attributes specific to this. To create a truly comprehensive approach to the highway safety problems associated with speeding and inappropriately high speeds, agencies should consider including a variety of strategies as candidates in any program planning process. Appropriate strategies may be of five types:

• Public Information and Education Programs (PI&E)—Many highway safety programs can be effectively enhanced with a properly designed PI&E campaign, which includes coordination with media outlets. The primary experience with PI&E campaigns in highway safety is to reach an audience across an entire jurisdiction (or a significant part of it). However, it may be desired to focus a PI&E campaign on a location-specific problem, such as an individual corridor with a history of severe crashes that have involved speeding. While this is a relatively untried approach compared with area-wide campaigns, use of roadside signs and other experimental methods may be tried on a pilot basis.
  
  Within this guide, PI&E campaigns, where application is deemed appropriate, are usually used in support of some other strategy. In such a case, the description for that strategy will suggest this possibility (in the exhibits, see the attribute area for each strategy entitled "Associated Needs"). In some cases, where PI&E campaigns are deemed unique for the emphasis area, the strategy is explained in detail.
• Enforcement of Traffic Laws—Well-designed and well-operated law enforcement programs can have a significant effect on highway safety. It is well established, for instance, that an effective way to reduce the occurrence of crashes and their severity is to have jurisdiction-wide programs that enforce an effective law against driving under the influence of alcohol (DUI), or driving without seatbelts. When that law is vigorously enforced with well-trained officers, the frequency and severity of highway crashes can be significantly reduced. This should be an important element in any comprehensive highway safety program.
  
  Enforcement programs, by the nature of how they must be performed, are conducted at specific locations. The effect (e.g., lower speeds, greater use of seatbelts, and reduced impaired driving) may occur at or near the specific location where the enforcement is applied. This effect can often be enhanced by coordinating the effort with an appropriate PI&E program. However, in many cases (e.g., speeding and seatbelt usage) the impact is area-wide or jurisdiction-wide. The effect can be either positive (i.e., the desired reductions occur over a greater part of the system), or negative (i.e., the problem moves to another location as road users move to new routes where enforcement is not applied). Where it is not clear how the enforcement effort may impact behavior, or where it is desired to try an innovative and untried method, a pilot program is recommended.
  
  Within this guide, where the application of enforcement programs is deemed appropriate, it is often in support of some other strategy. Many of those strategies may be targeted at either a whole system or a specific location. In such cases, the description for that strategy will suggest this possibility (in the exhibits, see the attribute area for each strategy entitled "Associated Needs"). Since there are situations where enforcement programs can be designed or enhanced specifically for speeding, there are strategies that discuss this in detail.
• Strategies to Improve Emergency Medical and Trauma System Services—Treatment of injured parties at highway crashes can have a significant impact on the level of severity, survival rate, and length of time an individual spends in treatment. This is especially true when it comes to timely and appropriate treatment of severely injured persons. Thus, a basic part of a highway safety infrastructure is a comprehensive and well-based emergency care program. While the types of strategies that are included here are often thought of as simply support services, they can be critical to the success of a comprehensive highway safety program. Therefore, for this emphasis area, an effort should be made to determine if there are improvements that can be made in how emergency medical services interact with other safety programs, especially for programs that are focused upon location-specific (e.g., corridors), or area-specific (e.g., rural areas) issues.
• Strategies Directed at Improving the Safety Management System—There should be a sound organizational structure in place, as well as an infrastructure of laws, policies, etc., to monitor, control, direct, and administer a comprehensive approach to highway safety. It is important that a comprehensive program not be limited to one jurisdiction, such as a state DOT. Local agencies often have jurisdiction over a large portion of the road system and are responsible for its related safety problems. They know, better than others, what the problems are. As additional guides are completed for implementation of the AASHTO Plan, the guides may address the details regarding the design and implementation of strategies for improving safety management systems.
• Strategies Detailed in Other Emphasis Area Guides—Several of these objectives, and many of the corresponding strategies, are applicable to other emphasis areas. Strategies that overlap between various guides in this NCHRP Report 500 series are discussed briefly in this section, and the other guides (as noted) should be referenced for more details. For example, there are treatments for speeding that would improve safety for all intersection users. Any program targeted at the safety problem covered in this guide on speeding should be created with consideration given to potentially appropriate strategies in these other guides.

Objective A—Set Appropriate Speed Limits

The primary purpose for setting speed limits is to promote highway safety. In addition to safety considerations, decision makers must balance mobility against a need to provide road users with access to adjacent land. Thus, the posted legal limit informs motorists of the maximum driving speeds that decision makers consider reasonable and safe for a road class or highway section under favorable conditions. In addition, speed limits provide the basis for enforcement. Well-conceived speed limits provide law enforcement officers and courts with an indication of appropriate speeds for favorable conditions and thus help target enforcement and sanctions on those who drive at speeds that are excessive for conditions and likely to endanger others (Milliken et al., 1998).

Statutory speed limits, set by federal, state or local government with jurisdiction over roads, are general limits that apply to a given type of roadway. This encourages uniformity in speed limits as well as removes the need to perform engineering studies to determine speed limits for every section of roadway. In many cases, the statutory speed limit is the most appropriate speed limit, but in some situations the statutory limit may not be ideal. In these cases, studies are performed to determine the most appropriate limit for those speed zones. The 85th percentile speed of the current traffic is measured, and the speed limit is initially set at this level. When other factors, such as crash history and traffic and pedestrian volumes, are considered, it may be determined that the 85th percentile speed is not ideal, and the speed limit may be adjusted. A properly set speed limit prompts a reasonable balance between mobility (travel time) and safety (fewer crashes and conflicts) for a certain road class or a specific highway section (Lu et al., 2003).

Other factors should be considered when establishing appropriate speed limits. These are particularly important if a full speed study is not being conducted or if the speed limit is being established for a highway on new alignment or a highway under significant reconstruction that is not yet under traffic.

• What is the type or functional class of the highway (i.e., freeway, arterial, collector, local)?
• Is the roadway setting urban, suburban, or rural?
• What is the adjacent land use? What is the type and amount of development?
• What is the amount of access along the highway? What is the level of access control? Are certain movements restricted by medians or other methods?
• What is the design speed?
• What is the highway geometry—horizontally, vertically, and the cross section?
• What are the speed limits on adjacent roadways?
• What is the crash history? Have there been speeding-related crashes or crashes involving pedestrians?
• What is the level of pedestrian usage?
• Is parking allowed along the street or highway?
• Are there difficult-to-perceive risks or driving demands or violations of driver expectancy (e.g., isolated curves, heavy vehicle traffic)?

All of these issues define the roadway environment and subsequently provide guidance in choosing a speed limit that is reasonable for the typical, prudent driver.

Roadways classified as principal or minor arterials are primarily intended to provide for through traffic, in contrast to collector or local streets that mostly serve abutting land uses. The higher type facilities (arterials), which generally carry heavier traffic volume and traverse areas of commercial/industrial land uses, will usually warrant a higher speed limit than collector or local streets. For the latter, the adjacent land uses (i.e., residential, school zone, or playground); access density; and special users (i.e., pedestrians and bicyclists) dictate a slower safe speed.

Setting speed limits too high may be a contributing factor to an increase in the frequency and severity of crashes. Likewise, there are adverse effects when speed limits are set too low. This objective aims to set appropriate speed limits as a proactive approach to preventing the occurrence of speeding-related collisions on new or existing roads.

Strategy A1—Set Reasonable and Prudent Speed Limits That Account for Roadway Design, Traffic, and Environment (T)

In determining appropriate speed limits for each road type, decision makers should be guided by both the likely risks imposed on others by individual driver speed choices and the availability of information to enable drivers to make appropriate speed choices. They should take enforcement and practicality into consideration. The 85th percentile speed is widely recognized as the most used analytical method for selecting the posted speed limit. The basis of setting the speed limit near the 85th percentile speed is to include as many people traveling at or below the speed limit as is reasonable. Maximizing the number of people traveling at a similar speed helps to minimize speed differentials and conflicts between vehicles. In addition to the 85th percentile speed, decision makers should also request technical information on the following four factors to help guide their determination of appropriate legislated speed limits for a specific road class (Milliken et al., 1998):

• Design speed, that is the design speed of a major portion of the road, not of its most critical design features (e.g., a sharp curve);
• Vehicle operating speed, measured as a range of 85th percentile speeds taken from spot-speed surveys of free-flowing vehicles at representative locations along the highway;
• Safety experience, that is crash frequencies and outcomes; and
• Enforcement experience, that is, existing speed tolerance (i.e., allowance for driving above the posted speed limit) and level of enforcement.

Setting speed limits not only needs to be carefully considered for new roads, but it is also important to periodically review speed limits on existing roads to ensure they are appropriate for the current conditions, especially when there has been a change in the land use, access or traffic characteristics.

The Manual on Uniform Traffic Control Devices (MUTCD) offers the following guidance on evaluating speed limits on existing highways (MUTCD, 2003):

At least once every 5 years, State and local agencies should reevaluate non-statutory speed limits on segments of their roadway that have undergone significant change in roadway characteristics or surrounding land use since the last review . . . . When a speed limit is to be posted, it should be within 5 mph (10 km/h) of the 85th percentile speed of free-flowing traffic.

The process to select the appropriate speed limit should also give consideration to unique or unusual design, traffic, or other environmental issues such as school zones, high percentage of trucks, heavy pedestrian volumes, frequent access or a concentration of elderly pedestrians. For more information, see http://www.mutcd.fhwa.dot.gov.

The speed limit for many new roads may already be defined by a state or local statute (i.e., statutory speed limit for residential areas). However the traffic, design and environmental characteristics of the roadway should still be considered to ensure that the roadway is appropriate for this general speed limit. An engineering study may determine that a speed zone should be established providing a different speed limit for a particular section of a road, or may identify changes in the roadway design to encourage drivers to travel at the appropriate speed. For example, a residential street with a wide cross section and sidewalks with large setback from the travel way may encourage higher speeds than intended by the speed limit, given the desired roadway setting and use. It may be desirable to alter these aspects of the design to encourage lower speeds to better match the context of the facility. See Exhibit V-2 for more information.

EXHIBIT V-2
Strategy Attributes for Setting Reasonable and Prudent Speed Limits That Account for Roadway Design, Traffic, and Environment (T)

Strategy A2—Implement Variable Speed Limits (T)

Several other countries such as the Netherlands, Germany, Sweden, and Australia have also tried VSL (Hines and McDaniel, 2002). VSL in Germany have been more widely accepted by the public than fixed speed limits (FHWA, 1995). Surveys have indicated that German drivers prefer roads with VSL, as it informs them of appropriate travel speeds, and other factors such as congestion, crashes, and lane closures. See Exhibit V-3 for further information.

Signs should be posted informing drivers of a reduced speed limit, but periodic enforcement will likely be needed to encourage drivers to slow down as they enter the area.

Strategy A3—Implement Differential Speed Limits for Heavy Vehicles if Appropriate (High Speed Only) (T)

EXHIBIT V-3
Strategy Attributes for Implementing Variable Speed Limits (T)

Objective B—Heighten Driver Awareness of Speeding-Related Safety Issues

Strategy B1—Increase Public Awareness of Risks of Driving at Unsafe Speeds (T)

Educational materials have been developed by several organizations for use in public information campaigns as well as for use by the general public. The National Highway Traffic Safety Administration (NHTSA) has such materials available for download from its website or in printed format. NHTSA's Traffic Safety Materials Catalog (http://nhtsa.gov/ people/outreach/media/catalog/Index.cfm) includes brochures, pamphlets, books, fact sheets, posters, reports, stickers, CD-ROMs, etc. Additional materials from other sources are described below under the heading "Information on Current Knowledge Regarding Agencies or Organizations That Are Implementing This Strategy."

Educational programs and activities are good methods for informing young and inexperienced drivers. This is one of the most important groups to target, as less experienced drivers are often unaware of many of the risks associated with speeding, and the potential repercussions of driving at an unsafe speed. NCHRP Report 500, Volume 19: "A Guide for Reducing Collisions Involving Younger Drivers" provides more information on targeting this age group with information and education campaigns.

An agency may wish to target drivers of a specific roadway with an information campaign if speed is a contributing factor in crashes on a specific portion of that roadway. An example is the Virginia Highway Safety Corridor Program, discussed further in Strategy C1, where specific segments of Virginia highways are designated as safety corridors and increased fines and enforcement are used to target corridor-specific safety issues.

Elements of a jurisdiction-wide campaign would be applicable to a broader range of issues over a much larger area and the methods for implementing such a campaign would likely differ from a corridor-specific campaign. An agency may choose to incorporate variable message signs, billboards, or highway advisory radio to distribute information for a program of this type. See Exhibit V-4 for more information.

EXHIBIT V-4
Strategy Attributes for Increasing Public Awareness of Risks of Driving at Unsafe Speeds (T)

Information on Current Knowledge Regarding Agencies or Organizations That Are Implementing This Strategy

NHTSA created a Traffic Safety Marketing website that provides numerous references and ideas available for organizations to publicize the risks of speeding. Sample posters, billboards, radio spots and television advertisements are available on the website to provide ideas: http://www.trafficsafetymarketing.gov.

Advocates for Highway and Auto Safety is an organization comprised of consumer, insurance, and health and safety groups. Their primary objective is to improve awareness of safety issues and support federal and state policies that target traffic safety. The group has a website with safety information concerning speeding and related safety issues: http://www.saferoads.org/index.htm.

The Insurance Institute for Highway Safety primarily observes vehicle safety features and their effectiveness in the event of a crash. They have material available online concerning safety and speed related collisions: http://www.iihs.org/safety_facts/safety.htm.

Strategy B2—Increase Public Awareness of Potential Penalties for Speeding (T)

Appealing to a driver's concern for his/her own personal safety or informing of the risks (Strategy B1) associated with driving at unsafe speeds may be effective in addressing the issue of speeding with some drivers. However, for others, appealing to their pocketbook is the most effective means of changing behavior. Penalties for excessive speeding, including fines, points, potential loss of license and delay of full licensure in graduated licensing programs can be deterrents to speeding behavior. In addition to civil penalties, car insurance companies may charge their customers more after receiving citations for unsafe driving behavior. Making drivers aware of the direct costs associated with excessive speeding, whether directly related to a crash or not, can be an effective strategy.

As mentioned previously, one of the most effective ways to communicate potential speeding penalties is through education and information campaigns. The media can demonstrate potential penalties for speeding and provide examples of specific instances where such penalties were enforced. Newspaper and television news agencies are good sources for relaying information such as heightened speeding enforcement efforts and speeding penalties. Some local newspapers in smaller communities have a public safety log, with a description and driver information concerning accidents and traffic-related violations, such as speeding. This is an effective way to inform the public of such penalties, and can have a deterrent effect as well. School systems, particularly high school driver education courses, provide opportunities to educate younger drivers on local speeding penalties.

Differences in Speeding-Related Penalties

A variety of penalties can be imposed as a consequence of speeding. The most common penalty for drivers exceeding the posted speed limit is a fine, which is issued by the local police department and highway patrol officers. Laws governing speeding vary by state and local municipalities; however, it is important to inform drivers that they are susceptible to a speeding ticket if they are exceeding the speed limit, no matter by how little.

Although enforcement and penalties are not the only reason that drivers should not speed, this seems to be a deterrent, at least when the threat of being penalized is apparent. There are several studies based on surveys that indicate that the presence of enforcement can indeed reduce travel speeds. One particular study in Australia observed law enforcement presence and speeding behavior. Surveys from the study found that repeated law enforcement presence on roadways can reduce the proportion of speeding vehicles on a roadway by approximately two-thirds (Armour, 1986). The study also found that within moments following exposure to law enforcement officers, drivers tended to increase to their normal travel speeds when they felt the law enforcement presence was no longer visible. Based on results from this and similar studies, one can assume that people sometimes recognize the risk of a penalty, rather than safety risks.

Penalties vary depending on the state law. NHTSA has an online table indicating penalties and state laws for speeding violations (http://www.nhtsa.dot.gov/PEOPLE/INJURY/ enforce/speedlaws501/summary_table.htm). Most states do not issue tickets exceeding $100 to first-time offenders (depending on state and local laws and the circumstances for which they were cited). However, depending on the circumstances, even first-time offenders can face jail time anywhere from 10 to 90 days. Drivers who are speeding and sanctioned with reckless driving, racing, under the influence of drugs or alcohol, or are repeat offenders are subject to increased fines, jail time, and license suspension. In cases where excessive speeding and reckless driving result in fatalities, drivers are subject to being charged with offenses such as vehicular manslaughter. In extreme cases, jail time and fines can be very high.

There are several approaches to monitor and deter repeat speeding offenders who regain or have not lost their licenses. One such method includes striping license plates; this has been used in some states for persons who are caught driving without a valid license. License plate striping is mentioned in NCHRP Report 500, Volume 2: "A Guide for Addressing Collisions Involving Unlicensed Drivers and Drivers with Suspended or Revoked Licenses." This method has been a proven strategy in certain states to minimize illegal driving. This method can be applied to repeat offenders of speeding violations, such that they would receive a striped renewal sticker to place on their license plates. These stickers would serve as indicators (and reminders) to law enforcement and the driver that he/she is a repeat offender. The public should be informed of such programs, in order to convey the message that a fine may not be the only penalty for serious speeding offenses. Exhibit V-5 provides more information on this subject.

EXHIBIT V-5
Strategy Attributes for Increasing Public Awareness of Potential Penalties for Speeding (T)

Strategy B3—Increase Public Awareness of Risks of Not Wearing Seatbelts (T)

Informing the public of risks associated with driving at unsafe speeds was identified in Strategy B1 as one effective approach in heightening driver awareness of speeding-related safety issues. The risks associated with not wearing seatbelts are also an important aspect to highlight in public awareness campaigns. Though increased seatbelt use is not directly related to a reduction in speeding-related crashes, it is closely related to a reduction in serious injuries and fatalities as a result of speeding-related crashes. NCHRP Report 500, Volume 11:"A Guide for Increasing Seatbelt Use" covers strategies for increasing the use of seatbelts; therefore, an overview of the information is presented in this guide, and Volume 11 should be referenced for additional information.

In Volume 11, three objectives were identified for the occupant restraint area:

1. Initiate programs to maximize use of occupant restraints by all vehicle occupants;
2. Ensure that restraints for children of all ages are properly used; and
3. Provide access to appropriate information, materials, and guidelines for those implementing programs to increase occupant restraint use.

The information in Strategy B1 of this guide, though written in the context of programs related to speeding, also applies to public information campaigns on the importance of seatbelt use. Information to convey to the public, which may help convince reluctant drivers to wear their seatbelts, could include the average seatbelt use rate for the targeted area and statistics on the improved chances for surviving crashes when restraints are used.

Strategy B4—Implement Neighborhood Speed Watch/Traffic Management Programs (Low Speed Only) (T)

Establishing a neighborhood speed watch committee, and posting signs alerting drivers to "watch their speed," can draw drivers' attention to their speeds as they travel through neighborhoods. Anecdotal evidence from law enforcement programs indicates that drivers speeding through neighborhoods are often people that reside in the neighborhood, and a traffic management program can provide information and education on the neighborhood level.

Neighborhood Traffic Management Programs

Neighborhood Traffic Management Programs (NTMPs) are being created all across the country. Cities develop these programs to assist residents in creating traffic management plans for their neighborhoods. This allows residents to provide input into traffic management issues in their communities. Through these programs, the city provides citizens with the resources to pursue solutions to their neighborhoods' traffic problems. Citizens are encouraged to create a neighborhood traffic safety committee. This committee will become the face of the neighborhood when dealing with the city government on traffic safety issues and can serve to facilitate communication between transportation departments when discussing traffic management options for a neighborhood. These committees are not only the liaisons between the neighborhood and the city, but they also can act as educators to the public. Public awareness campaigns are often started by neighborhood and community traffic safety committees, and are a way that residents can be involved in ensuring that their neighborhoods are a safe place for drivers, pedestrians, and bicyclists alike. The National Highway Traffic Safety Administration (NHTSA) has also created a helpful guide to starting a traffic safety committee. It is targeted towards a community wide committee but may also be useful to neighborhood committees as well. See http://www.nhtsa.dot.gov/portal/nhtsa_static_file_downloader.jsp?file=/staticfiles/DOT/NHTSA/Traffic%20Injury%20Control/Articles/Associated%20Files/810915.pdf for more information. Also, the NHTSA website is a valuable resource for information on speeding in general, as well as anti-speeding campaign materials.

Pace Car Program

Some Neighborhood Traffic Programs also include programs that encourage safe driving. One popular program is the Pace Car Program (Salt Lake City Corporation, 2000). The Pace Car Program is a citizen-based initiative that started in Boise, Idaho, and is being implemented in cities across the country, like Salt Lake City, Santa Cruz, and Boulder. The idea is quite simple: the program uses cars to calm cars, merely by encouraging motorists to abide by existing laws. The two elements of this program are a bumper sticker and a pledge. Pace Car drivers pledge to drive within the speed limit, stop to let pedestrians cross, walk when they can, and do something to their car to make others smile, with the goal of calming drivers rather than streets. They turn their car into a "mobile speed bump." Pace car drivers set a prudent pace for the drivers behind them. If they drive within the speed limit, the cars behind them will do the same. The central core of this program puts the responsibility to drive responsibly in the hands of the motorists. In many cities the Pace Car Program is intended to be a city-wide program, however all the programs specifically emphasize obeying the speed limits and watching for pedestrians on residential streets.

Neighborhood Speed Watch Program

The Neighborhood Speed Watch Program is another program that encourages safe driving. Speed watch programs are used to address the issue of speeding along residential streets. It is a public awareness program involving the residents of the neighborhood. Typically the concerned residents will request that a speed watch be completed. These programs have been implemented in communities across the country, including in Seattle and Bellevue, Washington, Colorado Springs, and Salt Lake City. See City of Bellevue, Neighborhood Traffic Services (http://www.ci.bellevue.wa.us/traffic_calming.htm) for more information.

In Salt Lake City, Neighborhood Speed Watch Program requests are handled by the Transportation Division of the Salt Lake City government. The program was developed in Salt Lake City due to the frequent requests to address the speeding problem on residential streets. Once a request has been made, the Transportation Division loans a radar unit to one of the residents for a 48 hour period. The resident and one other person will then record the speeds of vehicles using the radar unit. Other information, such as license plate number of speeders and time and date of the offense is also noted. This information is then returned to the Transportation Division where it is processed. A letter from the Transportation Division is then sent to the registered owners of all matched vehicles. The letter advises them of the observed speed violation and asks them to encourage drivers of their vehicle to drive within the speed limit when traveling on neighborhood streets. No speeding citations are issued. The Salt Lake City Speed Watch program is fairly typical of all Neighborhood Speed Watch programs throughout the country, with slight variations existing (see Exhibit V-6).

EXHIBIT V-6
Strategy Attributes for Implementing Neighborhood Speed Watch/Traffic Management Programs (T)

Strategy B5—Implement Safe Community Programs (T)

The Safe Communities program model was developed by the National Highway Traffic Safety Administration (NHTSA). A Safe Community is one that promotes traffic injury prevention by involving citizens in addressing key problem areas. Data determines the focus areas and guides the implementation of programs. A multifaceted approach to each problem area includes interventions in each of the four E's—Education, Enforcement, Engineering and Emergency Medical Services. The Safe Communities approach represents a new way community programs are established and managed. All partners participate equally to develop solutions, share successes, assume risks, and build a community structure and process to improve the quality of life in the community through the reduction of injuries and costs. A Safe Community establishes community ownership and support for transportation injury prevention. In doing so, it expands resources and partnerships, and increases program visibility throughout the community.

The concept behind a Safe Community is that of collaboration. Many Safe Communities are coalitions. The coalition is made up of concerned citizens, law enforcement, medical staff, and educators combined with existing community groups and programs that have similar missions to that of the Safe Community. One organization typically cannot handle all the traffic safety problems that face a community—but a coalition has a better chance at success. A key to the success of a Safe Community is community involvement. Engaging these other community groups and public entities is critical to its success. The Safe Community concept can be implemented on many different levels. It has been proven effective on the state, county, and community level. Examples of successful programs are the statewide program in North Dakota and a county program in Wright County, Minnesota. The North Dakota program provides resources and information for community programs and coalitions throughout the state. Their website (http://www. safecommunities.org) has a wealth of information available to community programs around North Dakota and the country. Safe Communities of Wright County (http://www. safecomm.org/) was formed in 1997 as a collaborative effort focused on reducing crashes in Wright County, Minnesota, through safety education and prevention. They have chosen to target commuters traveling on 55-mph roadways, and younger drivers. Driver inattention and speeding are two crash factors being targeted by this program. See Exhibit V-7 for further information.

EXHIBIT V-7
Strategy Attributes for Implementing Safe Community Programs (T)

Objective C—Improve Efficiency and Effectiveness of Speed Enforcement Efforts

Speed enforcement plays a large role in deterring drivers from traveling at excessive speeds. There are numerous methods that some law enforcement agencies currently use or are in the process of implementing in order to improve the efficiency and effectiveness of enforcing speed limits. Due to limited resources, the use of available funding and enforcement officers needs to be as efficient and effective as possible in order to have the greatest effect on highway safety.

Strategy C1—Use Targeted Conventional Speed Enforcement Programs at Locations Known to Have Speeding-Related Crashes (P)

Speed enforcement programs are launched by local and/or regional enforcement agencies. Speed campaigns typically target speeders through public awareness programs, as well as increased enforcement, providing increased enforcement at locations where a review of current travel speeds, crash history, and officer and public input show the potential for improvement. When used in conjunction with public education/awareness campaigns to increase knowledge of enforcement efforts, speed enforcement programs have the most potential for deterring drivers from speeding.

When starting a speed enforcement campaign the enforcement agency, or agencies, administering the campaign should first focus on specific roads to target, when they should be targeted, and why they chose those particular locations and times. Typically speed enforcement programs identify roads to target based on review of crash history, speeding citations, and public complaints. Several road segments can be identified and prioritized based on speeding trends and past crash reports. Performing enforcement during the times of day when speeding has been most prevalent in the past or when safety issues are most likely will help increase the effectiveness of the program.

Consistent speed enforcement can be effective in deterring drivers from speeding. The more a driver is exposed to law enforcement presence, the less he/she is likely to speed. In the article, "The Effect of Police Presence on Urban Driving Speeds," Armour found that increased law enforcement presence does have an impact on travel speeds. The author's literature review concluded that there was good evidence that the presence of law enforcement will reduce vehicle speeds and that this reduction can be maintained for at least some time after the vehicles have passed the zone of law enforcement presence. The author also discussed the possibility of a "memory effect." A memory effect of enforcement is produced if drivers reduce their speed in areas where they have previously seen the presence of the law enforcement officials. It has been shown that a memory effect of enforcement can be produced in highway situations using high levels of enforcement, and in urban situations, this effect may last up to 2 days after the law enforcement presence has been removed (Armour, 1986). However, the study discussed in this article indicates that the deterrent effect of law enforcement presence is often location specific for most drivers on urban roads (less than 40 mph), in that they decrease travel speeds at locations where they know or think law enforcement might be present (based on previous experiences), but speed up after the enforcement zone. This can have a negative impact, as drivers may choose to travel different routes where law enforcement presence is less common. This emphasizes the importance of reevaluating the areas in need of law enforcement on a regular basis. As drivers choose different routes, based on law enforcement presence, speeding may become an issue at other locations. This should be monitored and adjustments in enforcement made as needed. This also indicates a need for a greater number of law enforcement, if an area-wide problem exists.

Public involvement and awareness of special speed enforcement programs result in elevated effectiveness of the program by enhancing the deterrent effect of enforcement. Public awareness campaigns can result in an enhanced deterrent effect. Vigorous publicity that accompanies an enforcement program may provide as many measurable results as the enforcement itself. The public involvement campaigns that accompany these enforcement programs do not necessarily need to be spearheaded by the enforcement agency. In fact, law enforcement agencies do not typically have the resources to generate the level of public awareness needed to create the general deterrence effect needed for the success of the program. Many communities, however, have concerned citizens and civic leaders who have both the talent and resources that are required to develop and implement effective program support activities.

There are a number of special enforcement programs that target an area-wide traffic safety problem. These programs target a number of different safety issues, including speeding.

NHTSA has a set of guidelines for developing a municipal speed enforcement program, available online at http://www.nhtsa.dot.gov/people/injury/enforce/program.htm. It provides guidance to both law enforcement and concerned citizens to assist with the development of traffic safety program support committees and the implementation of municipal speed enforcement and other special traffic safety programs. These implementation techniques were tested in both Modesto and San Bernardino, California. These communities, as a result of the programs they established, experienced declines in speeding-related crashes (For more information, see NHTSA, http://www.nhtsa.dot.gov/people/injury/enforce/program.htm). Both communities participated in a 6-month NHTSA study. Each community conducted speed enforcement programs in six special enforcement zones, while a third community refrained from implementing any special enforcement effort to act as a comparison site. In addition to increased enforcement, San Bernardino and Modesto organized safety program support committees to elevate public awareness of the special enforcement program. These committees were comprised of local leaders, concerned citizens, a law enforcement manager, and chaired by emergency department physicians. The public campaigns were widespread and covered every area of the media. The public campaign included press conferences, posters, brochures, bus bench display advertising, media events, and television and radio public service announcements (NHTSA, 1995). Both communities experienced a decrease in speed-related crashes, with San Bernardino being the most successful with a decrease of 11.3 percent over the 6 month period, while Modesto had just a 1.1 percent decrease. However, the comparison site had an increase in crashes of 3.4 percent, increasing the statistical significance of both study sites' decrease in crashes.

As an added benefit to the increased enforcement, both communities experienced a decline in other serious crimes. Larceny-theft crimes declined 11–12 percent in both communities, while statewide it decreased about 1.7 percent. Traffic enforcement stops conducted during this study resulted in more than 2,000 arrests for offenses ranging from assault to misdemeanor and felony warrants (NHTSA, 1995). These results stress the importance of "looking beyond the ticket" and serve as an added benefit of increased speed and traffic law enforcement. Albuquerque, New Mexico, experienced similar results in the Safe Streets Program in 1997.

The Smooth Operator Program, in the Washington, DC metropolitan area, has been combating aggressive driving since 1997. This program is both an education and enforcement program that has brought law enforcement agencies, trauma experts, government officials, and other professionals together to educate motorists about the risks involved with aggressive driving, and to stigmatize this behavior on the roads of Maryland, Virginia, and Washington, DC. Speeding is a major component of aggressive driving, especially excessive speeding. The enforcement component of the Smooth Operator Program takes place in four law enforcement waves, throughout the year. Each wave is 1 week long and vigorously targets speeding and aggressive drivers (Smooth Operator website). Similar programs are discussed further in the NCHRP Report 500, Volume 1: "A Guide for Addressing Aggressive-Driving Collisions." For more information on this specific program visit: http://www.smoothoperatorprogram.com/ about.html.

In Virginia, the State Police, the Department of Motor Vehicles and the Department of Transportation have combined to develop a Highway Safety Corridor Program to address safety in high-crash locations on interstate and primary roads. Segments of interstate roadways have been identified as having higher than expected crash rates along with crash severity. The program development is an ongoing process as the agencies are currently in the process of establishing the Highway Safety Corridors based on crash data and public comment around the state. In 2004, a 15-mile stretch of Interstate 81 (I-81) near Roanoke was designated a Highway Safety corridor. A telephone survey in 2005 revealed that one-half of the residents were aware of the designation and 40 percent of those who were aware of the designation had said they improved their driving behavior as a result. Prior to the designation of the safety corridor, the number of crashes on I-81 had consistently increased each year from 2000 to 2003. The number of crashes has leveled off since the stretch was designated in early 2004 (see Virginia DOT, http://www.virginiadot.org/comtravel/cthighway-safety-corridor.asp). Highway Safety Corridors are discussed further in NCHRP Report 500, Volume 20: "A Guide for Addressing Head-On Collisions".

Another special law enforcement effort is saturation programs. The California Highway Patrol (CHP) often targets specific stretches of highways throughout the state to saturate with enforcement and engage in zero tolerance speed enforcement. On a given day, enforcement levels may be tripled to enforce this zero tolerance for speeding. Typically this special enforcement is conducted about 4 or 5 days each month, though it varies by area. Zero tolerance for speeding means the speed limit is strictly enforced. Anyone speeding, even just a few miles over the speed limit, can be pulled over and given a citation or warning. The primary goal of an enforcement saturation program is to increase the visibility of law enforcement, which is a deterrent for many would-be speeders. This generally decreases the average flow of traffic on busy roadways and therefore decreases the frequency and severity of crashes (Taylor, 2004, Hall, 2003).

These types of education and enforcement programs are an effective tool in increasing public awareness of the risks of driving at unsafe speeds, as discussed further in Strategy B1 of this guide; also see Exhibit V-8 for more information.

EXHIBIT V-8
Strategy Attributes for Using Conventional Speed Enforcement Programs at Locations Known to Have Speeding-Related Crashes (P)

Strategy C2—Implement Automated Speed Enforcement (T)

General Description

Law enforcement officers are not able to enforce speed limits on all roads at all times, and automated enforcement technologies offer the opportunity for increasing enforcement efforts and public perception that speeding citations are likely. The use of cameras to enforce red-light running is common practice in some jurisdictions, but their extension to applications involving speeding is more limited. Current technology can be used to deter drivers from speeding, and document them while traveling at speeds in violation of the posted speed limit. Such technology can be used without the presence of a law enforcement officer, if laws permit such use. This is ideal for high-speed roads where speeding is an issue that enforcement officials have difficulty controlling or on multi-lane roads with heavy traffic moving in both directions where it is often dangerous for officers to make traditional stops. Legislation enabling the citation of drivers recorded on camera is often needed for the technology to be employed. Studies in the United States indicate that speed cameras have been effective in reducing overall vehicle travel speeds and the proportion of drivers traveling in excess of posted speeds. However, it is common for the public to react negatively to the use of camera enforcement technology. Public involvement efforts are a significant portion of the implementation plans for automated enforcement programs.

Automated speed enforcement (ASE) devices are also known as speed cameras or photo radars. These devices comprise a speed measurement unit and a camera that work together to locate and identify drivers traveling at speeds above the posted speed limit. Speed cameras are generally located on roads with speeding issues and a history of speeding-related crashes. They are also often used in school zones, work zones and areas with large pedestrian volumes. The speed measurement unit on the camera measures the travel speed of vehicles on the roadway. When it detects vehicles exceeding the speed limit by a predetermined amount, the camera takes a photograph of the vehicle and records relevant information such as the travel speed, date, and time that the speeding violation took place. The speeds at which photo speed measurement units are triggered are determined by local enforcement agencies.

International Experiences with Automated Enforcement

Several countries report positive experiences with automated enforcement from both the traffic safety improvement and public acceptance perspective. Various reports published by the Federal Highway Administration and Transportation Research Board, as well as reports by researchers in the countries using automated enforcement, document these experiences.

Automated speed enforcement combines radars with cameras to photograph speeding vehicles and issue tickets. About 75 countries rely on cameras to enforce speed limits, which reduces high travel speed and crashes (IIHS, 1999). The Insurance Institute for Highway Safety (IIHS) states that in some countries automated enforcement generates the majority of the speeding citations. In the United Kingdom, one-half of all the speeding citations resulted from automated enforcement.

British officials introduced an electronic system using loop detectors in all lanes to detect traffic volumes and speeds. Roadside processors analyze the data to detect where traffic is slowing and this information is used to post variable speed limits—ranging from 20 to 60 mph—on electronic signs. Speed limits are set to produce a uniform and safe traffic flow based on traffic and other conditions. When no variable limit is posted electronically, the speed limit reverts to the national maximum of 70 mph. Without proper enforcement, simply posting variable limits would not be effective in managing speeds. Enforcement is achieved by mounting cameras across the highway to detect and photograph speeding vehicles. First a radar measurement is taken, and speeding vehicles are photographed twice, each photo a half second apart. The distance traveled between the two photos is used to confirm the radar measurement. There were 28 percent fewer crashes involving occupant injuries during the first year of the program, and property-damage-only crashes went down 25 percent. Preliminary data for the second year indicate the improvements are being maintained (FHWA, 2005).

A study tour for speed management and enforcement was conducted by the FHWA in 1995. The tour observed automated enforcement devices in the Netherlands, Germany, Sweden and Australia. It was observed that photo radar devices were used to a certain extent in all of the countries visited. However, in each country the photo radar devices were used in conjunction with a law enforcement officer presence (FHWA, 1995). The reasoning for using ASE devices with law enforcement presence is to ensure that such devices are not used solely as revenue generators—a common allegation from people opposed to the use of ASE devices. The study found that implementation of photo radar was most successful in the Netherlands and Australia. The success, in both countries, is credited to the fact that legislation was enacted requiring citations be sent to the owner of the vehicle rather than the driver (FHWA, 1995). Currently, no equipment is commercially available that will consistently and reliably identify the driver of the vehicle. Consequently, the study team recorded that photo radar devices were not successful in Germany and Sweden; this is because laws in these countries require that tickets must be issued to the driver of the vehicle rather than the owner (FHWA, 1995). The speed management study team reported that photo radar devices were most successful when used with informational speed management programs/campaigns.

Overall, the FHWA study tour found that speed cameras were less effective in Germany, due to the current laws requiring positive identification of the driver. However, German officials did perform a long-term study in the 1970s on the A3 autobahn that did not require the driver's identification and the results were significant. In general, the autobahn does not have a speed limit, except in urban areas. Prior to this study at Elzer Mountain, between Cologne and Frankfurt, there was no posted speed limit on this hilly stretch of the autobahn. In 1971, before the study was conducted, 80 to 95 percent of passenger vehicles exceeded the recommended roadway design speed, 15 percent of which exceeded 150 km/h (93 mph) in the left lane and 135 km/h (84 mph) in the middle lane, and 15 percent of trucks exceeded the design speed. In 1972, to reduce accidents and accident severity in this area, a 100 km/h (62 mph) speed limit was posted for passenger vehicles in the left and middle lanes and 40 km/h (25 mph) speed limit was posted for trucks in the right (truck) lane and a year later speed cameras were installed above each lane. The speed camera photographed all passenger vehicles exceeding the speed limit by 10 km/h and all trucks exceeding the truck speed limit by 5 km/h. The owners of the vehicles that were photographed were sent citations by mail. In addition to the speed cameras, law enforcement patrolled the segment of road to cite drivers for speeding. Immediately following the posting of the 100 km/h speed limit, a 30 km/h (19 mph) reduction in the average speed was observed. Following the installation of the speed cameras, an additional 20 km/h (12 mph) reduction in average speed was observed. The combination of setting a speed limit and the use of speed cameras resulted in a 91 percent reduction in crashes on that stretch of the autobahn. Ten years later, the reduced crash rate and lower speeds were considered sustainable. Just 7 percent of passenger vehicles in the left lane, 3 percent of passenger vehicles in the middle lane, and 10 percent of vehicles in the truck lane (right lane) were detected by the speed camera at speeds greater than 110 km/h for passenger vehicles and 45 km/h for trucks (Lamm and Kloeckner, 1984).

Another interesting automated enforcement method used in European countries is based on a concept of point-to-point automated speed enforcement. A product called the Speed Enforcement Camera System (SPECS) is a video system with automatic number plate reading digital technology consisting of two cameras. Each camera is set at a distance apart making it a speed-controlled zone. As a vehicle passes the two cameras its number plate is digitally recorded along with the time of entry and exit. The computer then calculates the speed based on the time and distance. This information is then transmitted to a central office or stored on discs in the cabinets at the roadside. If vehicles exceed the average speeds, a speeding violation is automatically generated. As the whole technology is digital it can run 24 hours a day with no film to change. Studies show that it has reduced fatalities in places where it was installed and also improved compliance with speed limits.

See Appendix 1 for further discussion on international experiences with automated speed enforcement.

Domestic Experiences with Automated Enforcement

As of April 2006, automated speed enforcement technology is used in about 20 communities in the United States (IIHS-Automated Enforcement Laws). Many jurisdictions that use automated enforcement are in states that have laws authorizing its use; however, not all states where automated enforcement is in use have such laws. Most automated enforcement programs and laws are for red light running; however, the use of automated enforcement for speed is increasing. The state laws that do exist vary from state to state; some authorize enforcement statewide, whereas others permit use only in specified communities. As of April 2006, New Jersey, West Virginia, and Wisconsin are the only states that prohibit any use of camera devices for enforcement purposes. Elsewhere in the United States, 25 states had no legislation regarding the use of any form of automated enforcement device, and 22 states and the District of Columbia had some legislation allowing the use of automated enforcement devices, either statewide or in select communities (IIHS-Automated Enforcement Laws).

There have been few studies in the United States that focus on the use of automated speed enforcement on high speed roads. A majority of the studies have been done in high-traffic, low-speed urban areas, like Washington, DC. They are also used in high pedestrian areas, where speeding is a serious issue, such as school and work zones. The studies that have been done in the United States indicate that speed cameras have been effective in reducing vehicle travel speeds. A study in 2002 found that speed cameras in the District of Columbia helped to reduce the number of vehicles traveling at 10 mph or more over the speed limit at enforced locations by 82 percent. This study also found that average travel speeds at enforced locations declined by 14 percent within 6 months of the speed cameras' implementation compared to nearby control locations (Retting and Farmer, 2003). This study is discussed further in Appendix 1. Likewise, a study in Garland, Utah, found that installing speed cameras, in conjunction with media coverage, helped reduce average travel speeds by 14 mph and reduce collisions in a school zone (IIHS-Automated Enforcement Laws). It may also be a cost effective solution since most enforcement agencies are constrained by staffing and funding limitations.

The results of a 1993 study in Riverside, California were reported at the 1998 TRB Annual Meeting (Bloch, 1998). The study evaluated the effectiveness of both photo radar and speed display boards. It concluded that both photo-radar and speed display boards can be effective in reducing vehicle speeds. Photo-radar reduced mean speeds 5.8 miles per hour (mph) where baseline speeds averaged 34–35 mph in 25-mph zones. It is common for the public to react negatively to such devices. Issues such as privacy rights are of concern to opponents of photo enforcement devices (Milliken et al., 1998). State and Supreme Court decisions have found that driving on public roads is not protected under the 4th Amendment of the Constitution (Milliken et al., 1998). As noted above, another issue among the public is owner versus driver of the vehicle in violation. Since the person driving the vehicle may not be the owner, most jurisdictions rely on the owner to divulge the name of the driver of the vehicle. However, in most jurisdictions, if the owner refuses then the citation is issued to the owner.

One problem that may pose issues concerning photo radar devices is the increasing market of anti-photo radar devices. There are vehicle devices available to consumers which detect photo radar devices to provide advance warning for drivers. Likewise, there are products available which are much lower in cost than photo radar detectors, including license plate covers, or spray cans that contain materials which produce glare or result in distorted photos of a vehicle's license plate. These items result in photos where the license plate is not readable, making it impossible to impose a penalty. If automated speed enforcement devices are implemented by an agency, measures to deter use of such products should be taken; see Exhibit V-9 for further discussion of these and other related issues. The state of North Carolina has targeted these issues by approving a bill that prohibits drivers from driving with an obscured license plate (NCSL, 2004).

Strategy C3—Increase Penalties for Repeat and Excessive Speeding Offenders (T)

Drivers who repeatedly flout speeding laws are a significant contributor to overall safety risk. All drivers convicted of speed limit violations are subject to penalties as determined by state and local laws. State laws vary on policy concerning license suspension, increased fines, and possible jail time for repeat speeding offenders and excessive speeding offenders, but these are strategies that could possibly deter convicted speeders from speeding in the future.

Many states have laws that support increased fines for repeat offenders of driving under the influence of drugs or alcohol. For example, the state of Ohio increases penalties for repeat DUI offenders, with minimum fines, maximum license suspension time, and minimum jail time increasing with each successive conviction (Ohio Insurance Institute, 2001). Eleven states currently have increased fines for repeat speeding offenders. An increased fine is given to a driver who is cited for a speeding violation within a set timeframe (typically 1 year) of the previous citation. For instance, the state of California fines the first offense a maximum of $100, the second offense within 1 year of the first is fined up to $200, and any subsequent offense within 1 year of the first offense is fined up to $250 (NHTSA, 2001). Further, upon the second conviction of the offense of driving greater than 100 mph on a highway within 3 years of the prior offense the amount of the fine increases to $1,000 and 2 or more prior convictions within 5 years results in a fine of $1,500 (NCSL, 2006). Also, most states have a demerit point system, where each violation earns demerit points, based on the severity of the violation. These demerit points are given for all moving traffic violations. Once a driver reaches the point threshold their driver license is suspended or, if available, the driver is given the opportunity to attend traffic school.

Thirty-six states offer traffic school or driver improvement courses to repeat traffic law offenders. The use of these courses varies among those states. Some use it as a penalty, requiring a habitual traffic law violator whose license has been suspended to take the course prior to reinstating his or her driving privilege. Other states offer it as an alternative to license suspension or to reduce demerit points. However, most states that offer these alternatives limit their use to once per year (NHTSA, 2001). For a driver whose speeding convictions would put him/her at the point threshold for traffic school more than once in a given time period, driver license suspension or revocation may be a more prudent action. There is potential for such courses to act as a deterrent to drivers who do not wish to subject themselves to such a course. Also, these courses have the ability to educate those drivers who speed repeatedly and excessively, and inform them of the real dangers of speeding.

A common excessive speeding problem, especially among young adults in urban areas, is illegal street racing. Illegal street racing is a form of auto racing that takes place on the streets and freeways. Speeds in these street races can reach in excess of 200 mph. Law enforcement officers attempt to stop these races, but because of their frequency and the ability of racers to change locations easily, this is a difficult task. This is a specific speeding problem in many larger cities around the country. A program in San Diego has been developed to combat the issue of illegal street racing, by providing an alternative location. RaceLegal.com was formed in 1998 by a professor at the San Diego State University's Graduate School of Public Health. A coalition was initiated with a grant from the California Office of Traffic Safety. This grass roots coalition involved city/county government, law enforcement, Bureau of Automotive Repair, Superior Court, City Attorney, District Attorney, and county probation. In short this program provides safer and sanctioned track alternative races at San Diego's Qualcomm Stadium. Drivers even have the opportunity to race against law enforcement officers in these sanctioned races. This provides a positive forum for interaction with law enforcement. The officers use this opportunity to foster relationships with young people, and encourage them to drive with safety in mind, including persuading drivers not to street race, always use seatbelts, and to lead a sober lifestyle. This program also uses public awareness methods to maintain a high level of community awareness of the incidence of local illegal street racing, as well as other traffic safety issues, such as safety belt usage and DWI. The RaceLegal.com program has had great success in reducing illegal street racing tragedies. According to the program's website, from 2002 to 2005 there has been a 94 percent improvement in crash fatalities due to illegal street racing. For more information on the RaceLegal.com program see Appendix 2.

Increasing state fines/penalties for repeat offenders is a potential strategy that might deter drivers from committing repeat offenses. Likewise, state laws could impose license suspension and potential for jail time, depending on the extent of offenses committed. Increased fines and penalties potentially deter people from committing a first offense, and more importantly potentially deter people from speeding again. See Exhibit V-10 for more information.

EXHIBIT V-9
Strategy Attributes for Implementing Automated Speed Enforcement (T)

EXHIBIT V-10
Strategy Attributes for Increased Penalties for Repeat and Excessive Speeding Offenders (T)

Strategy C4—Strengthen the Adjudication of Speeding Citations to Enhance the Deterrent Effect of Fines (T)

Court systems play an important role in the enforcement process for traffic citations. When speeding citations are thrown out or penalties/fines are reduced, the court system is downplaying enforcement (Milliken et al., 1998). There must be an agreement between enforcement officials and judges on the circumstances for which speeding citations will be written and the penalties that will be imposed. Likewise, it is equally important for the judicial system to treat speeding violations consistently, which can be done by establishing and following sentencing guidelines (Milliken et al., 1998).

There are many publications such as books, guides, and websites that investigate loopholes in state and municipal laws enforcing speeding violations. As a result, there are drivers guilty of speeding who find ways to dodge fines or penalties. Adjudication to address such issues can deter a driver from speeding if he/she is aware of the law, its consequences, and the ability of the judicial system to support law enforcement. There are many instances where court judges reduce fines/penalties or drop them completely if they feel that penalties are too harsh for conditions as stated in the citation (Milliken et al., 1998). This reduces the incentive for law enforcement officials to enforce the limits, and in turn reduces the deterrent effect of speeding penalties. It is important that law enforcement officials and court judges come to an agreement on enforcing speed limits uniformly and remove inconsistencies in penalizing violators (Milliken et al., 1998).

Adjudication can be strengthened through judicial outreach programs. These can be elaborate nationwide programs, such as college training courses, or local/regional initiatives. There are a number of judicial outreach initiatives targeted towards judges who preside over, and prosecutors who prosecute DWI cases. Similar programs targeted towards judges who preside over speeding-related cases can be helpful in strengthening the adjudication of speeding citations. The purpose of these outreach programs is to educate prosecutors and judges about the importance of consistent penalties for speeding. This can be done by initially providing crash and other traffic data to exhibit the severity of the problem and thus the importance of consistently upholding fines and penalties to maintain the deterrent effect of said penalties. NHTSA, in collaboration with the Bureau of Justice Assistance, has identified similar strategies for "reducing obstacles to obtaining impaired driving convictions and applying sanctions in a consistent manner" which highlights the importance of consistent adjudication (NHTSA, 2003). In NHTSA's Report to Congress on the FY 2003 Expenditure of Funds for Judges and Prosecutors, they also highlighted key training programs that justices could take part in to prepare them for presiding over DWI and other traffic safety-related cases. Specifically the National Judicial College, a national judicial education and training institution, offers traffic safety courses developed with NHTSA funding (NHTSA, 2003).

Judicial outreach programs and training courses are educational tools that can be used to strengthen the adjudication of speeding citations, which in turn is expected to enhance the deterrent effect of fines and penalties. See Exhibit V-11 for more information.

EXHIBIT V-11
Strategy Attributes for Strengthening the Adjudication of Speeding Citations to Improve the Deterrent Effect of Fines (T)

Strategy C5—Increase Fines in Special Areas (T)

General Description

Traffic violations in places like residential areas, work zones, and schools present a dangerous condition for both the roadway users traveling through these places and also to the workers, children and pedestrians within that area. Often violations, such as speeding or failure to obey flagger signals, are a factor in crashes in many of these places.

One method for reducing violations of traffic laws is to enforce laws and make fines significant enough to be a deterrent, and to encourage the judiciary to apply them consistently. Improving the application of increased fines through more frequent visible enforcement activities will help change driver perception about the likelihood of being cited for violations. In addition to the possibility of being cited a large fine, the driver needs to have the perception that the fine will be large and the sanction will be upheld by the courts. Otherwise, the sanction will be reduced to the inconvenience of the court visit.

Forty-five states currently impose increased penalties for speed violations in work zones, and in some states those increased fines apply to all types of violations. Studies show that many drivers continue to violate the work zone speed limits in spite of these increased fines. Using a consistent approach to enforcing work zone traffic laws and adjudicating citations is a way to curb this trend. This will require seeking the cooperation of the judiciary. It can be facilitated by encouraging a partnership and making sure that judges understand the importance of this strategy for saving lives. More information on this strategy, with respect to use in work zones, is discussed in greater detail in NCHRP Report 500, Volume 17 (Work Zones) of this series.

Doubling the fines in school zones may be one of the ways to improve compliance of speed limits in those areas. Signs may be posted around the school showing the message that speeding fines will be doubled. Public information campaigns may also be conducted to educate people about the penalty of speeding in school zones. Without proper enforcement, long-term effects may not be seen. More frequent enforcement activity may change drivers' perceptions and adherence to speed limits. Washington State enacted a state legislation in 1996 doubling the fines for speeding in school crosswalk and playground zones after a survey showed that 50 percent of drivers were not complying with reduced school zone limits and also speeds in excess of 50 mph were observed during the survey. One-half of the amount collected through doubling the fines was used for improving school zone safety like installation of signs, replacing existing school zone crossing signs with new fluorescent yellow-green signage. Similar strategies can be applied in problem locations in residential areas, hospitals and places with large elderly populations and numbers of pedestrians.

Objective D—Communicate Appropriate Speeds through Use of Traffic Control Devices

Traffic control devices are the primary means through which drivers are made aware of traffic laws. The most basic device is the speed limit sign, informing drivers of the maximum allowable safe travel speed, under any conditions. Variable message signs (VMS) provide more personalized, current information. Active speed warning signs display current travel speeds to drivers, and are intended to deter drivers from speeding and make them aware of the appropriate speed. In-pavement techniques can also be applied to the actual roadway to encourage safer speeds. The placement, visibility, and maintenance of all traffic control devices are important features in effectively communicating speed limits clearly. Poorly placed devices can have a negative effect on safety, and increase the chances of speeding-related collisions.

Strategy D1—Improve Speed Limit Signage (T)

The placement, visibility, and maintenance of speed limit signs are important features in effectively communicating speed limits clearly. A speed limit sign that has been misplaced, has low visibility, or is not properly maintained can result in ineffective communication of speed limits, which consequently can fail to encourage drivers to obey the speed limit. This can in turn have a negative effect on safety, and increase the chances of speeding-related collisions.

Location and frequency of speed limit signs are two key elements to properly communicating the speed limit. Speed limit signs need to be consistently placed at the proper locations (for example, following major intersections), which will reinforce a driver's expectation of when to look for a speed limit sign. This is especially important if there is to be a change in the speed limit from one section of the roadway to the next.

If a speed limit change occurs at a location where a driver may not be expecting one, then adding speed reduction signs should be considered. Along extended stretches of roadway where there are no changes in the speed limit, additional signing is still important as a reminder to drivers and also to inform drivers that may have entered the roadway at a minor intersection.

In Minnesota, "Reduced Speed Ahead" signs are used to give advance notice of reduced speed limits when the reduction is 15 mph or more. In urban areas, where speed reductions to 55 mph or less are required, speed reductions signs are to be erected on both sides of the roadway. This is to be followed by supplemental speed limit signs mounted on both sides of the roadways through the reduced speed zone. Supplemental speed limit signs, through all reduced speed zones, should be placed at intervals approximately equal to 60 seconds of travel time at the posted speed limit. Signs may need to be spaced closer in urban areas due to the increased number of access points. Minnesota sets 10 miles as the maximum spacing between speed limit signs in rural areas. In urban areas a speed limit sign should be placed at each interchange for traffic entering the mainline (Minnesota DOT, 2004).

As with placement, the driver's ability to see the sign is highly important if the driver is expected to obey the speed limit. Two factors that may affect the visibility include the mounting details (i.e., Is the sign properly mounted so that it is in a driver's field of vision?) and letter/border size (i.e., Was the appropriate letter and border size chosen for the speed limit such that a driver can easily read the sign?). For more information regarding the proper mounting and sizing of speed limit signs, refer to the current MUTCD.

Often overlooked, the context of the environment around a sign can impact its visibility. In urban areas where traffic signs and commercial signs may be abundant, a driver may need additional assistance with locating the speed limit signs. This assistance may take on different forms, but possibilities include using larger signs and removing or relocating unnecessary signs.

The issue of maintenance is an important factor in a sign's visibility. Poor maintenance can result in reduced visibility through many forms, including tree and shrub growth, vandalism, and reduction of the sign's retro reflectivity. See Exhibit V-12 for more information about improving speed limit signage.

EXHIBIT V-12
Strategy Attributes for Improving Speed Limit Signage (T)

Strategy D2—Implement Active Speed Warning Signs (Including Truck Rollover Warnings) at High Risk Locations Where Excessive Speeds and Potential Conflicts Are Expected (T)

Active speed warning signs, also known as radar speed displays, speed display signs or speed trailers, are similar to variable message signs (VMS), except they have radar technology that determines the traveling speed of vehicles. Active speed warning signs are intended to deter drivers from speeding and improve awareness that they need to obey the posted speed limit. Travel speeds are detected and then displayed on the message board.

Depending on the type of speed sign, some are capable of displaying additional text, such as "Slow," or they completely blank out when vehicles are driving at excessive speeds. This blank-out feature is intended to discourage drivers from speeding excessively to test the capabilities of the sign or their own driving audacity.

Active speed warning signs are similar to variable message boards and photo radar devices. They are different from automated speed enforcement devices in that they do not take photos and are not used for enforcement purposes. These signs differ from variable message boards as they have the radar technology to detect actual vehicle speeds. Speed warning signs can be used permanently at a location, or mounted on trailers and moved to different locations for temporary use.

Speed warning signs can be used permanently at a location, or mounted on trailers and moved to different locations for temporary use. One type of permanently mounted sign, used by King County in Washington, features a 12-inch high fluorescent yellow-green readout and is the same overall size and style as the existing speed limit sign. They are placed directly below the existing speed limit sign on the same post. These signs are ideal for neighborhoods as they are relatively small and do not stand out visually as much as a portable trailer would.

A study of the effectiveness of speed warning signs on speeding (for a roadway with a 25 mph posted speed limit) was reported by TranSafety, Inc., in May 1998, in the publication, Road Injury Prevention and Litigation Journal. Conclusions from this report are based on the study, A Comparative Study of the Speed Reduction Effects of Photo-Radar and Speed Display Boards (Bloch, 1998). The use of a speed warning sign reduced the mean speed by 5.8 mph at the experimental site but had little effect 0.2 miles downstream (a 2.9 mph reduction in mean speeds). A speed warning sign used in conjunction with intermittent enforcement resulted in a 6.1 mph mean speed reduction at the experimental site and a 5.9 mph reduction in the mean speed downstream of the display.

The study found that speed warning signs were the major contributing factor in reducing the number of vehicles traveling at "excessive" speeds (i.e., at least 10 mph above the posted speed limit) by 34.9 percent (Bloch, 1998). The study also found that when used in conjunction with intermittent enforcement, speed display boards reduced the number of vehicles at "excessive" speeds by 31.8 percent (Bloch, 1998).

Speed display signs can be used as a deterrent to speeding, which may result in decreased speed-related crashes. Studies have found that these signs effectively contribute to decreased travel speeds while in place, with mixed long-term results. In combination with enforcement and other technology such as photo radar devices, speed display signs could have a greater potential to reduce speeding.

The technology for detecting vehicle speeds and providing a real-time warning to drivers can be applied to locations where there is a potential for heavy vehicle rollovers, such as a sharp curve. In addition to speed, warning systems may need to collect other information such as vehicle height and weight to determine the potential of a rollover crash. For information specific to the issue of speed warning signs as part of an interactive truck rollover warning system, refer to Strategy 12.1 E2 in NCHRP Report 500, Volume 13: "A Guide for Reducing Collisions Involving Heavy Trucks."

As in other community-wide solutions, such as traffic calming, highway and/or enforcement agency staff should host a neighborhood meeting to discuss the existing condition with interested parties and identify possible solutions. If active speed warning signs are the preferred mitigation method, an on-site investigation should be conducted to determine a physical range along the roadway where the signs would best meet the needs of the traveling public. See Exhibit V-13 for further discussion.

EXHIBIT V-13
Strategy Attributes for Implementing Active Speed Warning Signs at High Risk Locations Where Excessive Speeds and Potential Conflicts are Expected (T)

Strategy D3—Use In-Pavement Measures to Communicate the Need to Reduce Speeds (T)

This strategy relies on the use of perceptual and in-pavement techniques to encourage drivers to proceed at a safe travel speed. This strategy can be applied along a roadway segment as well as at locations such as intersection approaches, work zones, toll plazas, ramps, and so on.

Perceptual Pavement Markings

Perceptual pavement markings give the driver the illusion of traveling faster than his or her actual speed in order to decrease the driver's comfort at excessive speeds. At locations where drivers are expected to reduce their speed, such as the beginning of a school zone, approach to an intersection, entrance to a residential neighborhood, or prior to a sharp horizontal curve, a converging pattern of pavement markings can be used to give the perception to the drivers that they are increasing their speed if they fail to slow down at a sufficient rate. Pavement markings can also be used for other perceptual applications, such as to give the illusion of lane narrowing. This method is intended to reduce a driver's comfort at an excessive speed while proceeding through the markings, as a way to encourage deceleration. This type of treatment has potential applications along the entire length of a corridor.

Perceptual pavement markings are good candidates for roads where speeding is known to play a role in either crash frequency or severity. Furthermore, perceptual techniques are expected to reduce travel speeds without the need for increased enforcement, and should be able to affect driver behavior regardless of whether a driver is intentionally or unintentionally speeding. Perceptual pavement markings can also encourage drivers to decelerate at an appropriate rate on the approach to an area with a reduced speed limit (i.e., school or work zone or intersection).

Perceptual pavement markings have several advantages over traditional speeding countermeasures. First, the cost of applying perceptual pavement markings is very low; however, the pavement markings must be routinely maintained in order to prevent a decrease in their visibility. Second, perceptual techniques are also very flexible since they can be used to target speeding specifically in high-risk areas, or for the whole length of a corridor. Finally, this strategy can be used for areas where law enforcement is not readily available, or can be used in conjunction with law enforcement for increased speed reductions.

There are several different types of perceptual techniques. The following are examples of different perceptual pavement techniques that have been in use.

• Transverse Lines: Transverse pavement markings are dashed lines that span the width of a travel lane. These pavement markings can be used to create the illusion that lane widths aredecreasing or narrowing, an effect that is perceived when the driver is traveling at higher speeds. A study in Kansas found that using these pavement markings at work zones decreased speeds and reduced the variation in speeds, though the speed reductions were fairly small (Meyer, 2001).
• Peripheral Transverse Lines: Peripheral transverse lines are the same as the transverse lines discussed above but they are used at the edges of travel lanes rather than across the entire lane. A study, as cited in Katz's report Pavement Markings for Speed Reduction, found that peripheral transverse lines performed the same, and in some occasions better than, full-length transverse lines. Full-length transverse lines tend to decrease vehicle speeds upon entering the zone with transverse lines; however, vehicle speeds tend to rise again after time.
• Converging Chevrons: Chevrons can also be used in a converging pattern. This pattern is characterized by a series of chevrons on the pavement surface that are placed progressively closer together. The first chevrons encountered by a driver passing through the pattern are widely spaced; those later in the pattern are closer together. The intent of this pattern is to create the illusion that drivers are traveling faster than they really are and to foster the impression that the traffic lanes are narrowing. These are sometimes accompanied by a dashed edge line. This edge line may promote the perception in drivers that the traffic lane is narrower than it really is. This perception can encourage a driver to reduce his/her speed (Griffin and Reinhardt, 1995).

Speed reduction can be further enhanced when these perceptual pavement techniques are combined with other in-pavement measures like rumble strips—discussed later in this strategy.

The Manual on Uniform Traffic Control Devices (2003) provides guidelines on the use of pavement markings as well as details concerning standard colors, dimensions, and placement.

Additional information can be found on the use of perceptual pavement markings in the discussion for Strategy 15.1 A4 in NCHRP Report 500, Volume 6: "A Guide for Addressing Run-Off-Road Collisions."

Rumble Strips

In addition to perceptual pavement marking techniques, in-pavement strategies, such as rumble strips, can be deployed as a means to reduce vehicle speeds and/or prevent crash types where speeding may play a significant role, like a lane departure crash, or a transition from a high-speed zone to a low-speed zone. Rumble strips can also be used as a traffic calming tool in high pedestrian areas, such as neighborhoods and school zones.

Rumble strips are grooves installed in the road surface intended to draw drivers' attention to the roadway environment—either that the vehicle is drifting out of the travel lane, or that there is a situation ahead that requires more attention or deceleration. When a vehicle travels over a rumble strip, the driver is warned through the vehicle vibrations and the noise it produces.

There are three types of rumble strip applications.

• Continuous Shoulder Rumble Strips: This is the most common type of rumble strip that is typically applied to the shoulder of high-speed roads. These aim to prevent run-offroad accidents. The primary use of this type of rumble strip for speeding-related crashes is not to reduce vehicle speeds, but is instead to provide an additional warning to drivers leaving the roadway, especially those that are speeding.
• Centerline Rumble Strips: These are applied to the centerline of high-speed roads. Centerline rumble strips aim to prevent median crossing or head-on collisions. Again, this application's primary intent is not to reduce speeding (although they may provide the illusion of lane narrowing, which may slow drivers), but is instead to warn drivers they are crossing the centerline.
• Transverse Rumble Strips: These are used at intersection approaches, toll plazas, work zones, ramps, and extreme curves. The warning provided by the transverse rumble strips should help drivers recognize that they need to slow down, possibly even come to a complete stop depending on the situation.

For more information, see FHWA Research and Technology's Priorities, Market-Ready Technologies and Innovations, Rumble Strips at http://www.fhwa.dot.gov/rnt4u/ti/rumblestrips.htm.

Rumble strips are commonly applied on the side of rural roads to deter vehicles from leaving the traveled way, and are increasingly used at the centerline of high speed roads. On low speed roadways, transverse rumble strips are used to alert drivers of a speed zone transition. On a state highway, speed reduction will typically occur in a transition from rural to downtown conditions. Transverse rumble strips can be used on approaches to a main street where a speed reduction is desired and where speed limit or warning signs are already in place. They are used to target drivers that are inattentive, drowsy/fatigued, careless, or distracted (FHWA Research and Technology). Rumble strips are also safety measures during adverse weather conditions. Fog, snow, rain and related weather events can reduce the visibility of pavement markings and road signs (FHWA Research and Technology). Rumble strips have the advantage in these types of conditions of not relying on visibility to be effective; however, some states paint rumble strips to increase their visibility during favorable conditions (FHWA Research and Technology).

Intersections, work and school zones, neighborhoods, toll plazas, and freeway ramps are all locations that are vulnerable to speeding-related collisions and pose risks to drivers, workers, or pedestrians. Rumble strips are low-cost measures that can be taken to prevent collisions at these locations, by providing warning and increasing awareness of changes in the road environment to drivers.

NCHRP Report 500, Volume 6: "A Guide for Addressing Run-Off-Road Collisions" provides supplemental information on the application of shoulder rumble strips to decrease run-offroad collisions, while NCHRP Report 500, Volume 4: "A Guide for Addressing Head-On Collisions" provides a review of centerline rumble strips to prevent head-on crashes. Both of these strategies are again reviewed in NCHRP Report 500, Volume 7: "A Guide for Reducing Collisions on Horizontal Curves." The use of transverse rumble strips was also reviewed in depth in NCHRP Report 500, Volume 5: "A Guide for Addressing Unsignalized Intersection Collisions." For additional information on the application and issues for rumble strips, refer to the mentioned guides.

Traffic operation personnel should consider rumble strips that are compatible with motorcycle and bicycle use. An abrupt rise in the roadway can present problems to bicyclists and motorcyclists. For this reason, there should be provisions made for cyclists to safely traverse through or around raised rumble strips. See Exhibit V-14 for more detail on this issue.

EXHIBIT V-14
Strategy Attributes for Using In-Pavement Measures to Communicate the Need to Reduce Speeds (T)

Strategy D4—Implement Variable Message Signs to Display Information on Appropriate Speeds for Current Conditions, As Well As Technologies to Monitor Conditions (High Speed Only) (T)

Variable message signs (VMS) are used to provide drivers information concerning the current and expected driving conditions. VMS display messages to drivers that will inform or warn them of conditions ahead that may prove beneficial to their safety or travel time. Examples of information commonly displayed by VMS are:

• Traffic conditions
• Work zone/construction areas
• Weather and surface conditions
• Detour/direction information
• Crashes and incidents
• Appropriate speed limits

VMS displays provide advanced technology to indicate safe travel speeds to drivers. For certain conditions (i.e., congested roadways or inclement weather), the posted speed limit may not be a safe travel speed; however, drivers will often attempt to drive at the posted speed limit despite the safety problems this may create. A key element to this strategy's effectiveness is the support from enforcement and adjudication when speed limits are decreased due to conditions.

In addition to using ITS to display a safe speed for the driving conditions, ITS technology is needed to collect information on current conditions so that speed limits can be accurately set. Traffic conditions can be observed using video cameras and/or pavement loop detectors. Video can also be used to observe weather conditions, along with weather stations. Furthermore, in-pavement sensors are available for collecting information on actual pavement conditions, including pavement surface condition and temperature. Often this information can be gathered and then sent to a central location, such as a traffic management center in a large metropolitan area, for processing and display on VMS. See Exhibit V-15 for more information on how to use VMS.

EXHIBIT V-15
Strategy Attributes for Implementing Variable Message Signs to Display Information on Appropriate Speeds for Current Conditions As Well As Technologies to Monitor Conditions (T)

Objective E—Ensure Roadway Design and Traffic Control Elements Support Appropriate and Safe Speeds

While drivers have a responsibility to drive at a safe speed, they need to be able to receive clues from the roadway environment on what that speed should be. The design of a roadway and its traffic control devices should consider the speeds at which the agency wishes people to drive, as well as the speeds that can reasonably be expected.

A key element in safety is that road design and traffic control elements effectively communicate appropriate and safe speeds to ensure the safety of road users. This objective observes several different design and traffic control elements that are vital in providing safe travel at high speeds, and aims at correcting locations where current design elements are not appropriate. Strategies for this objective include:

• Combinations of geometric elements to control speeds
• Safe speed transitions through design elements
• Adequate sight distance for expected speeds
• Speeds on approaches to reduced speed zones
• Appropriate intersection design for speed of roadway
• Adequate clearance intervals at signalized intersections
• Appropriate operation of traffic signals for speed of intersections and corridors
• Protected-only signal phasing for left turns at high-speed signalized intersections
• Lighting at high speed intersections and high volume pedestrian/bicycle crossings
• Reduction of traffic speeds and volumes with traffic calming and other related countermeasures

Strategy E1—Use Combinations of Geometric Elements to Control Speeds (Horizontal and Vertical Curves, Cross Section), Including Providing Design Consistency along an Alignment (T)

Designing a roadway to influence drivers to travel at a particular "controlled" speed, and discourage them from traveling at an excessive or inappropriate speed, helps to prevent crashes from occurring and can also reduce severity when they do occur. Geometric elements, such as horizontal and vertical curves, affect operating speeds, and these elements can be designed in combinations to encourage appropriate speeds. This strategy aims at providing consistency in the design of roadway elements and selecting design elements that can be used to control vehicle speeds while providing for safe travel. Such road design elements may include the alignment, number of lanes, and width of lanes and shoulders. The provision of design consistency leads to roadway elements that meet drivers' expectations and result in consistent speeds along an alignment and fewer unexpected speed changes, factors which contribute to a reduced likelihood of crash occurrence.

Of the several design factors that influence driver speed and perception, two of the primary ones are the curve radius and the tangent length. Other important parameters include the length of spirals, the vertical grades and curves, the available sight distance, and the crosssection features.

Historically, the horizontal curve is the most critical geometric design element that influences driver behavior and has the most potential for crashes, and research has indicated that the average accident rate for horizontal curves is about three times the average accident rate for highway tangents and the average run-off-the-road crash rate for highway curves is about four times that of highway tangents (Lyles and Taylor, 2006).

Reasons for this increased crash frequency include restricted sight distance, driver inattentiveness, and speed estimation errors. To mitigate errors by the driver, it is important to convey a message to the driver as to what is the appropriate speed of the roadway. This can be done by providing a roadway that conforms to what a driver expects (from previous experience) and also provides clear clues as to what is expected of her/him on a particular roadway. This strategy thus aims at being consistent in the design of the roadway elements and selecting design elements that positively influence driver behavior and expectations, resulting in safer driving speeds and thus a reduced risk of collision.

The concept of design consistency is well documented and it is recognized that a consistent alignment will enable most drivers to operate safely at their desired speed along the entire alignment. Designs should thus strive to provide alignments that meet driver expectations, and avoid or minimize unexpected, unusual, or inconsistent design or operational situations. For example, large differences and sudden changes in horizontal alignment should be avoided, as these tend to increase driver workload and increase the likelihood of crashes. This includes situations such as the unexpected introduction of a relatively sharp curve at the end of a long tangent, where the higher speeds that may be encouraged by the long straight alignment could lead to driver error when the curve is encountered. One strategy is to flatten the curve so that a driver can negotiate it at a higher speed which reduces the likelihood of someone over driving the curve. Research by Zegeer et al. (1992) indicated that curve flattening may reduce crash frequency by as much as 80 percent, depending on the central angle and the amount of flattening. Alternatively, providing a consistent design by the occasional introduction of a series of gentle curves may prevent speeds from getting too high on the tangent sections. This idea builds off the concept that is called a self-organizing road (Keith et al., 2005). Other design considerations include providing consistency in terms of sight distance availability, particularly to horizontal curves, again ensuring that the roadway meets the driver's expectations and does not surprise them (see Strategy E8).

A self-organizing road is essentially defined as a road that ". . . increases the probability that a driver will automatically select appropriate speed or steering behavior for the roadway without depending on road signs. The geometric features of the road encourage the desired driver behavior, and do not rely on the driver's ability or willingness to read and obey road signs." (Keith et al., 2005). The concept of a self-organizing, self-enforcing road is therefore to select distinctive features such that the appearance of the road leaves drivers in no doubt as to what sort of facility they are on. By providing a roadway that is planned and designed in such a way, an appropriate and "consistent" speed for each road category can be achieved. Distinctive features that "explain" the road include items such as number of lanes and lane width, presence or lack of cyclists and pedestrians, width of sidewalks, presence of medians, provision of on-street parking, and frequency of access. Simply, a self-organizing road is designed utilizing an aesthetic approach so that drivers will select an appropriate speed because it is comfortable and safe. In this way, the roadway environment provides positive enforcement by encouraging the driver to stay within the desired speed limit.

In addition to curvilinear alignments, other examples of a self-organizing road that can be used on low-speed roadways include lane width reduction (or lane narrowing), traffic calming measures, and roundabouts (Keith et al., 2005).

Narrower lane widths tend to reduce speeds since drivers are "encouraged" to slow down to maintain a comfortable position within the available lane width. Research carried out by an OECD Scientific Experts Group in 1990 reviewed impacts of lane width upon driver behavior and consistently found a reduction in speed with decreases in lane width and vice versa. Yagar and Van Aerde (1983) found that increasing lane width from 3.3 to 3.8 m was associated with a 2.85 km/h increase in speed. More recent work (Fitzpatrick et al., 2000) has corroborated these findings of very modest changes in speed associated with lane width.

Narrower lane widths can be implemented either by physically creating narrower travel lanes or by visually decreasing the available width, and may be supplemented by other measures within the driver's peripheral vision, such as landscaping and transverse lane markings, to reinforce the "slow down" message. This treatment may be a more effective tool for reducing speeds on rural roads and roads where there are more visual cues within the driver's peripheral vision.

As previously noted, the roadway width can be visually narrowed by such techniques as painting wider edge lines. The intention is that the driver will reduce speed to maintain a comfortable position within the narrower painted lanes. However, a study in a residential area by Lum (1984) indicated no impact on free speeds of narrowing lane widths from 5.5 m and 4.25 m to 2.7 m; thus, simply narrowing lane width without other measures, such as transverse lane markings that have the effect of attracting the driver's peripheral vision, may not be particularly effective.

Regardless of the design technique used, the key is a consistent design so that the driver is not presented with an unexpected situation; Exhibit V-16 illustrates this point.

EXHIBIT V-16
Strategy Attributes for Using Combinations of Geometric Elements to Control Speeds, Including Providing Design Consistency Along an Alignment (T)

Strategy E2—Effect Safe Speed Transitions through Design Elements and on Approaches to Lower Speed Areas (T)

Reduced speed zones are areas where posted speed limits are reduced to safely accommodate traffic, pedestrians, and road conditions because there is a risk increase (perceived or actual) if traffic continues to travel at higher speeds. Reduced speed zones are generally used in school zones, high pedestrian areas, work zones, intersections and highway transitions from rural to urban areas. Work zones and rural to urban transitions are the most common type of reduced speed zones on high speed roads (45+ mph) such as freeways or major arterial highways. Reduced speed zones further lower speeds on low speed roads; typical applications include school zones, high pedestrian areas, work zones, and in residential or commercial neighborhoods.

This strategy aims at methods to encourage safe and effective speed transitions on the approaches to (and within) areas with a reduced speed limit. It may not be possible to ensure that all vehicles drive at or below the reduced speed limit; however, there are several methods and countermeasures that can be deployed to deter speeding in these zones.

To increase the effectiveness of speed transitions, signing, enforcement, pavement markings, and other safety elements should be used appropriately to deter drivers from speeding in these zones. Further, roadway designs sensitive to the context in which they will be located can encourage appropriate speed choice by drivers. Elements of the roadway, such as curvature and lane width, along with landscaping and other roadside features, can communicate the context of the roadway. For example, areas with high pedestrian activity may include raised or otherwise marked crosswalks and other physical features that draw drivers' attention to the nature of the area, which can both reduce their speeds and increase their awareness of pedestrians in the area. Visual cues that may encourage drivers to reduce vehicle speeds on approaches to lower speed areas include the introduction of sidewalks and curb and gutter, raised medians, landscaping, ornamental lighting, pedestrian signs, textured crosswalks or intersection pavement, banners and decorations, and other forms of street furnishings.

• Enforcement: There are different enforcement measures that can be taken and the best type of enforcement to implement depends on factors such as the extent of the speeding problem and the resources available for implementation. Enforcement methods to control speeds at these locations include:
  • Increasing law enforcement presence
  • More frequent ticketing of violators
  • Increasing fines (doubling or tripling fines in reduced speed zones)
  • Employing enforcement technology such as automated speed devices (e.g., photo radar which can be used in conjunction with speed display signs)
• Transverse rumble strips: Rumble strips are used to gain a driver's attention by producing an alarming noise and vibration throughout the vehicle. The use of transverse rumble strips in reduced speed zones may not efficiently control driver speeds; however, rumble strips used in conjunction with traffic control devices can provide an increased awareness of the importance of reducing speeds.

  Depending on the topography and the ambient noise levels, rumble strips can generate considerable noise over a large area. Consequently, they can be a more appropriate application in a rural environment and have only limited use in urban areas. Speed reductions from the use of transverse rumble strips alone are likely to be small and probably erode over time.

• Advance warning signs: It is important to use signs to provide drivers with advance warning of reduced speed locations. Previous versions of the MUTCD used a regulatory sign informing drivers of decreases in the posted speed limit ahead. The 2003 MUTCD allows a yellow diamond warning sign with either text or an arrow to show a reduced speed zone is ahead and what the speed limit is in that zone. Variable message signs used to display messages informing drivers of reduced speed zones and other relevant information are good to use in construction zones. Active speed feedback display signs can also be used to control speeds at reduced speed zones, as they typically gain a driver's attention, especially when the signs are used in conjunction with photo radar devices for enforcement.
• Road design: Changes can also be made to the alignment and cross-section of the roadway as a method to inform drivers they need to reduce their speeds. These changes could be something as simple as introducing curb and gutter or using pavement markings to give the illusion of lane narrowing. Other strategies to slow drivers may include channelization, raised medians, allowing on-street parking, the introduction of curvilinear alignments and the extension of the urban environment further into the transition area (for example, by the use of landscaping and lighting). With these design countermeasures, it is important that they are introduced in such a way that they do not become or create a safety hazard.

The use of distinctive road design features such as those noted above help to identify a change in the environment and can influence the driver's speed approaching, and in, the transition zone. Reference should be made to the discussion on self-organizing roads under Strategy E1 for further information regarding the use of physical and visual measures to achieve appropriate speed behavior.

As well as their use as an effective method of intersection control, roundabouts are often used to reinforce a change in environment (e.g., rural to urban) in conjunction with a change in speed. The roundabout also provides an opportunity to provide a "Gateway"—a device to mark such a transition from a higher speed facility to an environment requiring a lower speed and greater driver attentiveness, particularly if the driver had been driving on the "faster" facility for a relatively long time. The use of roundabouts is discussed further under Strategy E3, including the importance of providing ample warning to enable the driver to effect a safe speed transition on the approach to the roundabout (for example by the introduction of a raised median "splitter" island, or the introduction of a curvilinear alignment). One non-geometric method used in the United Kingdom, and found to be effective in reducing collisions associated with speed adaption, is to apply yellow transverse bar markings on high speed approaches to roundabouts. The transverse markings are typically placed at decreasing intervals on the roundabout approach to affect the driver's visual field and encourage the driver to slow down. Details of the United Kingdom markings and their spacing are provided in Chapter 5 of the United Kingdom's Traffic Signs Manual. Earlier research on trial markings at 42 roundabouts in the United Kingdom showed a 57% decrease in speed related crashes over a period of 4 years (Helliar-Symons, 1981).

Although traffic calming measures are more typically associated with an urban type setting, there may be opportunities to use such techniques in a rural environment to encourage a reduction in speed. These techniques may include lane narrowing (physical or visual), installation of median islands and other forms of channelization, and changes to the roadway surface. These techniques can be used in combination to reinforce the message to the driver that there is a change in the environment requiring a speed adjustment. In the United Kingdom, "Gateways" exist in a wide variety of forms to influence the driver's behavior on the approach to an area requiring a lower speed and greater attentiveness. The primary feature is a conspicuous vertical element at the side of the road (for example, enhanced signing, often with yellow backing boards; countdown signs on the approach to the gateway; vegetation; walls and fences; etc.). Other elements typically incorporated include lane narrowing (visual or physical), colored road surfacing, and special pavement markings (for example, speed "roundels" and "dragon teeth" lane edge markings). Using these measures in combination, and in conjunction with good sight lines, generally improves the Gateway conspicuity and its effect on reducing speeds. However, care should be taken to avoid introducing additional hazards (such as non-yielding signs and other roadside features), and consideration should also be given to possible visual intrusion. Research in the United Kingdom (Wheeler et. al., 1994, Wheeler and Taylor, 1999) indicates typical average speed reductions of 1 to 2 mph from simple signing and marking; 5 to 7 mph from more comprehensive signing/marking with high visual impact; and about 10 mph with physical measures.

In another rural application (Steinbrecher, 1992), the district of Neuss, Germany implemented a combination of traffic calming measures on the approaches to 13 rural towns which included reducing the lane widths to about 5.5 m; adding strips of pavement stones to optically narrow the road further; installing refuge islands; and raising the road in asphalt. The road raising was achieved by constructing 3 m long ramps with slopes of about 35:1, which could be negotiated comfortably at speeds of 30 mph. Steinbrecher noted that the road raising aspect in combination with the refuge islands seemed to achieve the greatest effect of speed reduction. Results indicated speeds dropped in all 13 towns with before treatment speeds averaging between approximately 45 to 53 mph, and those after treatment averaging about 37 to 45 mph. The average speed reduction was just over 5 mph (varying between about 1 and 9 mph). The overall impact on average crash rate was a reduction from 1.1 per year to 0.6 per year.

Further information on traffic calming measures and their effectiveness is provided under Strategy E9 in this guide.

Construction zones are known to present increased challenges to drivers, as they typically form choke points requiring drivers to transition from a higher speed relatively unrestricted environment to a lower speed congested environment. This transition takes place on the approach to the work zone, and this area represents a particularly serious collision risk as some drivers do not respond well to the speed and lane changes that are required on the work zone approach, and often make unexpected or dangerous maneuvers. The key is to provide ample advance warning to enable drivers to reduce their speed on the approach to the work zone so that they can safely enter the zone and make any necessary lane changes or merges in a safe and efficient manner (it is also important that measures are implemented to guide drivers through the work zone itself). Reference should be made to the Manual of Uniform Traffic Control Devices and to NCHRP Report 350 for further information regarding the standardization of work zone areas in terms of traffic control and work zone safety devices. Volume 17 of the NCHRP Report 500 series, on reducing work zone fatalities, should also be referenced.

If a roadway has a speed transition into an area with a large number of pedestrians, possible design countermeasures include speed tables, pedestrian bulb outs, and raised crosswalks. These items are discussed in more detail in Strategy E3, Appendix 1, and Exhibit V-17.

EXHIBIT V-17
Strategy Attributes for Effecting Safe Speed Transitions through Design Elements and on Approaches to Lower Speed Areas (T)

Strategy E3—Provide Appropriate Intersection Design for Speed of Roadway (T)

Intersection design plays a large role in the safety of roads. According to A Policy on Geometric Design of Highways and Streets, "The efficiency, safety, speed, cost of operation, and capacity of the highway system depend on the design of its intersections" (AASHTO, 2004). The main objective of intersection design is to, "reduce the severity of potential conflicts between motor vehicles, buses, trucks, bicycles, pedestrians, and facilities, while facilitating the convenience, ease, and comfort of people traversing the intersections" (AASHTO, 2004). To provide safe intersections to road users, there are five elements that should be considered in the design (AASHTO, 2004):

1. Human factors
2. Traffic considerations
3. Physical elements
4. Economic factors
5. Functional intersection area

This strategy aims primarily at addressing traffic considerations and physical elements that apply to intersection design. Some of the important factors to consider for intersection design are the grade, angle, horizontal and vertical alignment, median type, turn lanes, corner radii, and traffic control devices at the intersection. See Appendix 1 for additional information on these design elements.

Roundabouts provide an important alternative to signalized and all-way stop-controlled intersections. Modern roundabouts differ from traditional traffic circles in that they operate in such a manner that traffic entering the roundabout must yield the right-of-way to traffic already in it. Roundabouts are a good option for low-speed roads, as they can serve moderate traffic volumes with less delay than signalized or all-way stop-controlled intersections because traffic can normally traverse the roundabout without stopping. It has been found that single-lane roundabouts operate more safely, and though not necessarily with fewer crashes, but with lower injury rates than two-way stop-controlled intersections. For further details regarding roundabouts, reference should be made to NCHRP Report 500, Volume 5.

Comprehensive details regarding the improvement of safety at both unsignalized and signalized intersections are provided in NCHRP Report 500, Volume 5 and Volume 12, respectively. Of particular relevance, the unsignalized intersection report (Volume 5) provides guidance on the choice of appropriate intersection control (Strategies 17.1.F1 through F3) and also on the use of geometric design improvements to reduce collision frequency and severity (Strategies 17.1.B1 through B18). The signalized guide (Volume 12) provides similar guidance (Strategies 17.2.B1 through B5). Because detailed discussion is contained in these other guides, the discussion in this guide will present an overview of speeding-related fatalities, and the other guides should be referenced for additional information. Also see Exhibit V-18 for further discussion of design issues.

EXHIBIT V-18
Strategy Attributes for Providing Appropriate Intersection Design for Speed of Roadway (T)

Strategy E4—Provide Adequate Change + Clearance Intervals at Signalized Intersections (P)

Change + clearance intervals are the portion of a signal between the end of a green phase and the beginning of the next green phase for a conflicting movement. (Note: The "change + clearance" interval will simply be referred to as clearance interval for the remainder of this discussion.) Clearance intervals should be designed to account for expected approach speeds in order to reduce the potential for red-light-running collisions. Clearance intervals that are too short can result in drivers not being able to stop in time for the red signal, and intervals that are too long can breed disrespect for the signal in drivers familiar with the intersection. Either situation can result in red-light running, which increases the risk for angle collisions, the severity of which is compounded by speeding. Clearance intervals provide safe transitions in right-of-way (ROW) assignment between conflicting streams of traffic. Clearance intervals can include both yellow and all-red timing between conflicting green phases. NCHRP Report 500, Volume 12: "A Guide for Reducing Collisions at Signalized Intersections" covers material on optimal clearance intervals in Strategy 17.2 A2; therefore, an overview of the information is presented in this guide, and Volume 12 should be referenced for additional information.

There is no specific standard for determining clearance intervals at an intersection. Clearance intervals are dependent on many factors, including operating speeds, intersection width, vehicle lengths, and driver characteristics such as reaction time and braking. ITE has developed an equation for determining the length of the change + clearance interval but some agencies may use a uniform clearance interval. See Appendix 2 of NCHRP Report 500, Volume 12: "A Guide for Reducing Collisions at Signalized Intersections" for more information on establishing clearance intervals. (http://safety.transportation.org/).

There are different issues with poor clearance intervals at high speed intersections. Clearance intervals that are too short in length result in drivers stopping abruptly, which may lead to rear-end collisions. Furthermore, a too short clearance interval could result in an angle collision involving vehicles traveling through the intersection after the end of a phase and vehicles entering the intersection on the subsequent phase. One study showed that the effect of clearance intervals shorter than those calculated using ITE guidelines had higher crash rates for rear-end and right-angle crashes (Zador et al., 1985). Clearance intervals that are too long may result in a growing problem of red-light violations as studies have suggested. For more information on yellow and all-red intervals refer to Volume 12 of this series, as well as Making Intersections Safer: A Toolbox of Engineering Countermeasures to Reduce Red-Light Running. (McGee, 2003). This can be accessed online at: http://www.ite.org/library/redlight/MakingInt_Safer.pdf

Strategy E5—Operate Traffic Signals Appropriately for Intersections and Corridors (Signal Progression) (T)

Traffic signals are timed and phased with the objective of providing efficient movement of traffic. The coordination of traffic signals, or signal progression, has been found to have many safety benefits. Signals that are properly coordinated produce platoons of vehicles that travel the road without having to stop at multiple signals. This results in less stopping and can be expected to reduce rear-end collisions at intersections.

Signal progression also improves turning movements at intersections. Signal progression creates platoons of vehicles, which creates more gaps in traffic and allows vehicles to make left turns and right turns onto the major street more easily. This is an important benefit for high speed roadways where larger gaps are needed for a vehicle to safely enter and accelerate, or cross the traffic stream. In addition, judging gaps at high speeds may be more difficult, especially for older and inexperienced drivers.

The topic of signal coordination is discussed in detail as part of Strategy 17.2 A4 in "A Guide for Reducing Collisions at Signalized Intersections" (NCHRP Report 500, Volume 12), and therefore the information is not repeated in this guide. The reader should refer to Volume 12 for additional details on this strategy.

Strategy E6—Provide Adequate Sight Distance for Expected Speeds (P)

Sight distance is a fundamental element in geometric design and reflects the driver's ability to see the road ahead and other road users so that the facility can be used in a safe and efficient manner. The amount of sight distance provided to the driver is a function of the threedimensional features of the highway—the cross-section (roadside), vertical alignment (grades and vertical curves), and horizontal alignment. The total sight distance requirement essentially comprises the distance traveled during two key events, often referred to as the perceptionreaction time and the maneuver time. The former refers to the time needed for a driver to recognize an object or condition requiring a response and deciding what action is required (e.g., initiating contact with the brake), and the latter refers to the time from the initiation of the vehicle response to the completion of the driving maneuver (e.g., from the time the driver applies the brake to the time when the vehicle comes to a complete stop). These time periods, and hence distances, will vary depending on vehicle speeds and the types of maneuvers being undertaken, for example, stopping, turning, or passing. Roads designed with insufficient sight distance for the expected speed can not always provide drivers with adequate time to identify a hazardous situation, decide on a course of action, and then complete their maneuver.

Sight distance at curves (horizontal and vertical), intersections, passing zones and areas where drivers have to negotiate through a complex or unexpected situation (i.e., lane drop, toll plaza, etc.) should account for the speeds expected in those locations. Providing adequate sight distance can reduce rear-end crashes involving vehicles stopping suddenly when the driver views something unexpected, angle crashes related to drivers accepting gaps that are too small for their turning maneuver, and head-on, passing-related crashes. Clearing sight lines, removing roadside objects that block views, and possibly flattening curves are potential solutions for improving sight distance.

More information regarding sight distance is provided in Strategy 15.2 A3 of Volume 7 on horizontal curves, Objective 17.1 C of Volume 5 on unsignalized intersections, and in Strategy 17.2 C1 of Volume 12 on signalized intersections, as well as in Exhibit V-19 of this guide.

EXHIBIT V-19
Strategy Attributes for Providing Adequate Sight Distance for Expected Speeds (P)

Strategy E7—Implement Protected-Only Signal Phasing for Left Turns at High-Speed Signalized Intersections (High Speed Only) (T)

Protected-only left turn signals have a phase designated specifically for left-turning movements (known to be one of the highest risk movements at intersections), which is indicated with a green arrow. Protected-only phases are applicable on high speed roadways and/or in high traffic volume situations, where there may be a lack of adequate gaps to complete turning movements. In addition to vehicle speeds and volumes, there are several factors that may warrant the use of protected-only "left turn" phases, such as delay, visibility, distance of the intersection, and safety at the intersection (e.g., crash history).

Benefits of protected-only left turns include increasing left-turn capacity and mitigating intersection delays for vehicles turning left (Brehmer et al., 2003). The use of protected left turn phases also improves safety by removing conflicts during a left turn movement. This characteristic can be especially important on high speed roadways where the prevailing speed can contribute to the crash severity and may play a role in the difficulty a driver has with identifying and selecting a safe gap.

Even though protected/permissive left-turn phases are warranted under certain conditions, this strategy focuses on protected-only left turn phases due to the increased safety benefits that can occur at high speeds.

To help in the selection of the appropriate left turn phasing (permitted, protected-only, and protected/permitted), several website sources that provide additional information on left turn signal phasing include:

• http://www.webs1.uidaho.edu/niattproject/
• http://www.dot.state.mn.us/metro/trafficeng/dsg_crse/chap21.html#_Toc429824696

Additionally, refer to NCHRP Synthesis 225, "Left-Turn Treatments at Intersections," for additional guidance on the type of left-turn phase to use (Pline, 1996).

Because protected-only left turn phasing was already reviewed as part of Strategy 17.2 A1 in "A Guide for Reducing Collisions at Signalized Intersections" (NCHRP Report 500, Volume 12), that guide should be referenced for an in-depth discussion of left turn phasing.

Strategy E8—Install Lighting at High-Speed Intersections (High Speed Only) (T)

High speed roads with unlit or poorly lit intersections, as commonly found in rural highways, can pose a hazard to drivers. Lighting is desirable at intersections of high speed roadways to provide drivers with adequate vision of other vehicles and obstacles which may pose safety issues, such as sight distance limitations, at intersection approaches. Intersection lighting has not been proven to prevent speeding nor is it intended to be a speed reduction strategy, but providing adequate lighting at high speed intersections is a proactive approach to avoiding collisions where speeding may play a role, particularly during nighttime and adverse weather conditions.

Studies have found that the installation of lighting at intersections is effective in reducing nighttime collisions. This strategy aims at preventing collisions along high speed roads, particularly at rural intersections by providing lighting. Lack of adequate lighting at high speed intersections can increase exposure to high severity collisions.

Because intersection lighting is discussed in detail in Strategy 17.1 E2 in NCHRP Report 500, Volume 5, "A Guide for Addressing Unsignalized Intersection Collisions," Volume 5 should be referenced for an in-depth discussion of lighting intersections.

Strategy E9—Reduce Speeds and/or Volumes on Both Neighborhood and Downtown Streets with the Use of Traffic Calming and Other Related Countermeasures (Low Speed Only) (T)

When implemented appropriately, traffic calming can alleviate speeding problems on neighborhood roads and downtown arterials, as well as on an area-wide scale. Divertive measures can control vehicular volumes on neighborhood roads by restricting access, and forcing vehicles to use the arterial roadways. There are many different traffic calming techniques that can be used to control vehicle speeds and are appropriate for low speed roadways. Descriptions of these strategies are described in more depth in NCHRP Report 500 Volume 10: "A Guide for Reducing Collisions Involving Pedestrians." Traffic calming may be applied at intersections, mid-block, or even along entire segments of a corridor.

When the purpose of a traffic calming measure is to control speeds, the specific traffic control device implemented may need to be repeated along the corridor. Otherwise, the drop in vehicle speeds is likely to be isolated to the vicinity of the device. Speeding traffic through residential neighborhoods is often a concern with the residents living in the area, especially when the traffic is (or at least is perceived to be) cut-through traffic. Drivers may choose to cut through a neighborhood to avoid busy sections of urban arterials, possibly even to avoid a single intersection, or to avoid residential collectors with existing traffic calming. When drivers leave higher speed arterials for the low speed residential streets, they may be unwilling to slow down and drive at the posted speed limit in the residential area. A combination of speed and volume control measures can help mitigate neighborhood speeds through either physical traffic calming elements, or by divertive/restrictive measures, which force vehicles to use the arterial roadways.

Jurisdictions across the country have implemented traffic calming measures to discourage drivers from using neighborhood shortcuts, and some have even prohibited vehicles from turning into residential areas by partially closing intersections or prohibiting access during peak periods. The goal of these approaches has been to make the shortcut a less attractive option or not an option at all. In doing so, it is important to improve the attractiveness (i.e., improving the operations) of the arterial streets or urban road system intended to provide mobility. This may be accomplished through a variety of measures, including adding through lanes, removing unnecessary signals, improving signal timing, and coordinating signal systems. These changes may involve improving a small area, or even a single intersection. However, changes may need to be implemented across a large portion of a system if there is significant congestion. For example, at a signalized intersection where vehicles are often delayed for more than one cycle length, consideration could be given to increasing capacity through the intersection by providing an auxiliary lane in advance of the intersection, and continuing it for sufficient distance downstream of the intersection to allow vehicles to adjust their speeds and safely merge back to the original lane configuration. Such a treatment should be implemented only where it will be clearly understood, and not where it may cause confusion to drivers which may introduce additional safety concerns.

Area-wide traffic calming programs implement these measures on a larger scale. Such a program could include conversion of one-way streets to two-way, or two-way streets to oneway; narrowing lanes; and installation of vertical and horizontal speed control measures on collectors and/or local streets throughout the area. Such programs have been tried in several European countries and in Japan, with some success in reducing vehicle speeds.

For further guidance, the Institute of Transportation Engineers provides a report entitled, "A Toolbox for Alleviating Traffic Congestion and Enhancing Mobility," which includes a section on potential solutions for application to urban arterials. Details of these solutions, including descriptions, implementation issues, benefits and costs, example applications, and references, are included in the document (Meyer, 1997).

The various traffic calming measures used to control speeds and volumes are described in Appendix 3, including those that mitigate speeds by altering vertical and horizontal paths of vehicles, as well as those that control volumes, especially along residential collectors, by diverting or restricting traffic. Some strategies are discussed in Exhibit V-20 of this guide.

EXHIBIT V-20
Strategy Attributes for Reducing Speeds and/or Volumes on Both Neighborhood and Downtown Streets with the Use of Traffic Calming and Other Related Countermeasures (T)