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Guidelines for right-turn lanes on urban highways
Abstract
Guidelines for the use of right-turn lanes at access points on urban two-lane and four-lane sections of the state highway system in Nebraska were developed in this research. The guidelines are based on the results of a benefit-cost analysis conducted over the range of conditions representative of those on urban sections of the state highway system in Nebraska. The guidelines define the design hour traffic volumes for which the benefits of right-turn lanes exceed their costs. The benefits used in the analysis were operational and accident cost savings they provide to road users. The operational cost savings were those associated with reductions in stops, delay, and fuel consumption experienced by through traffic. These operational effects were determined by computer simulation. The accident cost savings were those associated with the reduction in accidents expected from the lower speed differences between right-turning and through traffic provided by right-turn lanes. The relationship between speed differential and accidents established by Solomon (14) was used to estimate the reduction in rearend accidents that would be expected to result from the provision of a right-turn lane. The right-turn lane costs used in the development of the guidelines were typical right-turn lane construction costs on urban sections of the state highway system in Nebraska. These costs were computed as a function of roadway speed and right-of-way cost. The right-of-way costs used included zero for construction within the existing right-of-way and values representative of low, medium, and high urban right-of-way costs in Nebraska. The guidelines define the right-turn design hour volume required to justify a right-turn lane as a function of the following factors: (1) directional design hour volume, (2) roadway speed, (3) number of lanes on the roadway, and (4) right-of-way cost. The guidelines indicate that the right-turn design hour volume that warrants a right-turn lane is lower on roadways with higher directional design hour volumes and higher roadway speeds, because the road user costs associated with the operational and safety effects of right turns are greater on higher-volume, higher-speed roadways. Likewise, the right-turn design hour volume required to justify a right-turn lane on a two-lane roadway is lower than that on a four-lane roadway. Comparison with guidelines developed by others indicates that the guidelines developed in this research are within the range of existing guidelines. In addition, they are more definitive than the other guidelines because they account for the effects of roadway speed and right-of-way costs.
Subject Area
Civil engineering
Recommended Citation
Ataullah, Syed, "Guidelines for right-turn lanes on urban highways" (1993). ETD collection for University of Nebraska-Lincoln. AAI9331409.
https://digitalcommons.unl.edu/dissertations/AAI9331409