As high-speed roads approach urban areas, transition zones are usually provided to encourage drivers to reduce their speed to one that is appropriate for the urban road that they are entering. Managing speed with high-speed to low-speed locations is an important consideration for state and local agencies. Two recent reports, NCHRP Report 737 (Design Guidance for High-Speed to Low- Speed Transition Zones for Rural Highways) and NCHRP Synthesis 412 (Speed Reduction Techniques for Rural High-to-Low Speed Transitions) provide some insight into the effectiveness of specific treatments in safely reducing the speed of vehicles in the transition area. Despite these and other studies, NCHRP Report 737 concludes that “in the United States, design guidance for high- to low- speed transition zones for rural highways is in its infancy".
The proposed project is intended to study how driver performance (e.g., average speed, speed variance, and lane position) may be affected by different characteristics of transition zones, especially, with and without specific treatments. It will also examine whether driver performance may vary time of day, traffic conditions, and familiarity with the route. This study will also try to determine at what point in the high to low speed transition area does a driver's speed change, and what factors (e.g., speed limit signs, denser roadside development) are associated with a change.
The study locations will be identified through NCDOT's GIS layer with speed limit data. For these study locations, multiple sources of data will be compiled. One important source could be the SHRP2 naturalistic driving study (NDS) data. NDS provides speed and other driver performance data for every 0.1 second for vehicles that were equipped with the onboard technology. In addition, other sources of speed data including data compiled by NCDOT and vehicle probe data from INRIX, HERE, and NPMRDS, will be utilized. For some locations, speed data will be compiled from the field. Finally, crash data will be compiled to assess the safety impacts of these improvements. A final report will be prepared to document the complete research effort including the results of the literature review, selecting of study sites, acquisition of NDS and other data, analysis and evaluation results, and findings.