Evaluation of Innovative Approaches to Curve Delineation for Two-Lane Rural Roads


Run-off-road crashes are a major problem for rural roads. These roads tend to be unlit, and drivers may have difficulty seeing or correctly predicting the curvature of horizontal curves. This leads to vehicles entering horizontal curves at speeds that are too high, which can often lead to vehicles running off the roadway. This study was designed to examine the effectiveness of a variety of active and passive curve warning and curve delineation systems on two two-lane rural roads to determine which is the most effective at reducing vehicle speeds and assisting lane-keeping. The study consisted of a human-factors study, as well as an observational study. There were nine curves examined in the study on two road sections in Southwest Virginia. The human-factors study included participants whose speed and lane position were tracked as they drove through eight curves, both before and after new treatments were installed in each of the eight curves. The observational study examined the speed and lane position of traffic on all the curves before and after the installation of the new treatments. The observational study included a curve on a road near the primary study section. The results of the study were mixed, with every tested system leading to some reductions in speed or encroachments at some parts of the curve while also leading to increases in the same values at other parts of the curve. No clear difference was discovered between passive and active systems or between delineation and warning systems. The study recommends that in addition to a safety assessment, specific curve characteristics and budget should be the main considerations in the selection of a treatment for a curve.



Horizontal curves, Active and static warning signs, Speed and lateral placement, Delineations, On pavement signing


Gibbons, R. B., Medina Flintsch, A., Williams, B. M., Li, Y. E., Machiani, S. G., & Bhagavathula, R. (2018). Evaluation of Innovative Approaches to Curve Delineation for Two-Lane Rural Roads (No. FHWA/VTRC 18-R25). Virginia Transportation Research Council.