This emphasis area addresses head-on crashes associated with highway (i.e., nonintersection) segments. A head-on crash typically occurs when a vehicle crosses a centerline or a median and crashes into an approaching vehicle. A head-on crash can also occur when a driver knowingly or unknowingly travels the wrong way in a traffic lane. Head-on crashes occur as a result of a driver's inadvertent actionsas with run-off-road (ROR) encroachmentsor deliberate actionse.g., executing a passing maneuver on a two-lane road.
Statement of the Problem
The 1999 statistics from the Fatal Analysis Reporting System (FARS) indicate that 18 percent of noninterchange, nonjunction fatal crashes were two vehicles colliding head-on. The percentage was the same for 1997 and 1998 data. In addition, these data reveal that
The high percentage of head-on crashes on rural, undivided, two-lane roads might suggest that many head-on crashes relate to failed passing maneuvers. However, in nearly all cases, fatal head-on crashes occur in nonpassing situations. Of 7,430 vehicles involved in head-on crashes on two-lane, undivided roadway segments, only 4.2 percent involved a vehicle "passing or overtaking another vehicle" (1999 data). The corresponding percentage for rural roads was 4.3 percent. These low fatal-crash percentages are corroborated by two studies performed by the Federal Highway Administration's (FHWA's) Highway Safety Information System (HSIS). According to the studies, all crashes either were passing related or occurred in no-passing zones.
This does not imply that passing crashes should be excluded from a fatality-reducing program, just that strategies should likely be chosen to reflect that roughly 91 percent of the vehicles involved in fatal head-on crashes on two-lane, divided roadways are related to vehicles either "going straight" (68 percent of the total head-on fatalities) or "negotiating a curve" (23 percent of the total). Comparable percentages hold for the rural roads.
It might also be expected that a significant proportion of head-on collisions occur in construction zoneslocations where the traffic pattern is altered and opposing lanes may be brought closer together than normal. However, FARS data indicate that in 1999 only 1.9 percent of noninterchange, nonjunction head-on crashes (90 of 4,713) occurred in construction zones. While this problem could intensify with an increasing presence of work zones in the future, it is clear that programs aimed at reducing fatalities in head-on collisions should concentrate on "normal" highway sections.
These statistics indicate that most head-on crashes are likely to result from a motorist making an "unintentional" maneuverthe driver falls asleep, is distracted, or travels too fast in a curve. There may be other contributing factors, such as alcohol use or speeding.
Given these factors, affecting head-on fatalities is clearly more complex (and perhaps more difficult) than just providing adequate passing zones. Indeed, most head-on crashes are similar to ROR crashesin both cases, the vehicle strays from its travel lane. In cases involving unintentional maneuvers, the causes are likely to be very similar. Potential head-on crashes can become ROR crashes if there is no oncoming vehicle, and a ROR crash can become a head-on crash if the vehicle "overrecovers" into the opposing travel lane.
Programs and Strategies
The objectives for reducing the number of head-on fatal crashes are to
These objectives are similar to those cited for ROR crashes (emphasis area 15.1; see Volume 6 of this report, the ROR guide). The objective of reducing the severity of crashes is covered under the ROR emphasis area.
For each objective identified (except for the third objective, which is discussed in Volume 6 of this report, the ROR guide), there exist various strategies (Exhibit I-1). Each strategy is described in detail in this guide. Strategies may fall into either of two categoriestreatments implemented over extended sections of highway or treatments at selected spot locations.
Other Head-On Strategies
Other head-on strategies that are also ROR ones include the following (they are discussed in Volume 6 of this report, the ROR guide):
Another approach to addressing safety problems in a comprehensive way is to replace the independent activities of engineers, law enforcement personnel, educators, judges, and other highway safety specialists with cooperative efforts, an approach reiterated in these guides.