Comparison of SHRP2 Naturalistic Driving Data to Geometric Design Speed Characteristics on Freeway Ramps
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abstract
Current geometric design guidelines provide information to designers on appropriate design speeds for freeway entrance and exit ramps. These guidelines are based on practices developed several decades ago; however, it is not well known how well the speeds suggested by existing design guidance reflect current driving behavior and technologies. The Strategic Highway Research Program 2 (SHRP2) Naturalistic Driving Study (NDS) data provides an opportunity to analyze detailed driving data that did not previously exist, to critically review and potentially update existing design guidelines. The proposed project will obtain and analyze detailed data � speed profiles along with selected driver and vehicle variables � from the SHRP2 NDS dataset for portions of trips that occurred on and near freeway ramps. In addition to the SHRP2 data, the research will use information on the design characteristics of the ramps traveled during the SHRP2 study; the road data will be obtained from the RID dataset, plan sheets, and other available sources from the road agencies in the SHRP2 participating states (New York, Indiana, Florida, North Carolina, and Washington). Analysis of the data will compare NDS data and road data to identify relationships between the factors used to select freeway ramp design speed (e.g., radius, superelevation, etc.) and the actual speeds of drivers traveling on those ramps and their associated behaviors (e.g., brake/accelerator use, steering wheel angle, etc.). In addition to the research activities that will be documented through a typical research project report, the findings and conclusions will be reported through a doctoral dissertation. Further anticipated products include recommendations for revisions to the process for determining ramp design speeds in the American Association of State Highway and Transportation Officials (AASHTO) Green Book and related guidance documents, a description of how to conduct a similar study for other roadway features of interest, and suggestions for relevant updates to existing ramp speed prediction tools. Collaboration with a PhD Student from VTTI is anticipated for assistance with the SHRP2 Data Request.
