Horizontal Curves

Index of Strategies by Implementation Timeframe and Relative Cost

Exhibit IV-1 provides a classification of strategies according to the expected timeframe and relative cost for this emphasis area. In several cases, the implementation time will depend on such factors as the agency’s procedures, the need for additional right-of-way (ROW), and the need to follow environmental impact processes. The range of costs also may vary for some of these strategies depending on many of the same factors. Placement in the exhibit is meant to reflect the most commonly expected application of the strategy.

EXHIBIT IV-1 Strategies Classified by Relative Cost and Time Necessary for Implementation
Relative Cost to Implement and Operate	Strategy
Time Frame: Short (less than a year)
Low	15.2 A1 Provide advance warning of unexpected changes in horizontal alignment 15.2 A2 Enhance delineation along the curve 15.2 A3 Provide adequate sight distance^a 15.2 A4 Install shoulder rumble strips 15.2 A5 Install centerline rumble strips 15.2 A6 Prevent edge dropoffs^b 15.2 B2 Remove/relocate objects in hazardous locations^c 15.2 B3 Delineation of roadside objects
Moderate	—
Moderate to High	—
High	—
Time Frame: Medium (1–2 years)
Low	—
Moderate	15.2 A7 Provide skid-resistant pavement surfaces 15.2 A8 Provide grooved pavement 15.2 A9 Provide lighting of the curve 15.2 A10 Provide dynamic curve warning system
Moderate to High	15.2 A15 Prohibit/restrict trucks with very long semitrailers on roads with horizontal curves that cannot accommodate truck offtracking^d 15.2 B4 Add or improve roadside hardware 15.2 B5 Improve design and application of barrier and attenuation systems 15.2 A11 Widen the roadway^e 15.2 A12 Improve or restore superelevation 15.2 A14 Install automated anti-icing systems 15.2 B1 Design safer slopes and ditches to prevent rollovers
High	—
Time Frame: Long (more than 2 years)
Low	—
Moderate	—
Moderate to High	—
High	15.2 A13 Modify horizontal alignment
^aProviding adequate sight distance can be costly if it involves redesigning the vertical curvature of the roadway or cutting back the slope of a hillside. It is assumed here, however, that most sight obstructions will be longitudinal barriers such as trees or foliage that may be cut back at minimal costs. ^bThe action could be done in a short timeframe. However, it is assumed to be done at little extra cost as part of a regular repaving program. ^cRemoval/relocation of some objects (e.g., bridge abutments and drainage structures) can be costly, depending upon the object. It is assumed here, however, that most objects will be small appurtenances. ^dThis strategy is considered medium cost because it may consume a considerable number of staff-hours to develop such a policy and have it approved. ^eWidening the roadway does not necessarily require acquisition of additional right-of-way (ROW). If ROW is needed, the cost will be moderate to high, and the time required will be long.