A great debate is raging within the NCDOT and the public about four-lane divided versus five-lane undivided cross-sections for urban and suburban arterials. Four-lane divided cross-sections seem to be safer, based on collision rates from existing facilities in North Carolina (NC). Four-lane divided cross-sections are also more aesthetic and provide better midblock levels of service. However, five-lane cross-sections allow direct access from both directions into adjacent properties, and are thus favored by landowners, developers, and many local government officials. Five-lane cross-sections are narrower, and thus may save on construction costs. Five-lane cross-sections may also have safety and capacity advantages at some intersections due to fewer u-turns than with four-lane divided cross-sections.
The purpose of this project is to provide the NCDOT with the best possible up-to-date, NC-specific information on the rival cross-sections. The project team will calibrate a collision model for each type of cross-section using NC collision data. The collision model will include terms of driveway densities and other factors, which allow the model to make much more credible predictions about the safety of future roads than can be made currently using statewide collision rates. The project team will also collect operational and safety data at intersections on four-lane divided cross-sections where significant volumes of u-turns are present to see whether those u-turns actually cause the problems attributed to them.
The main product from the project will be a easy-to-use four-page brochure with the collision model, u-turn results, and other facts about the rival cross-sections. Planners, designers, local officials, and others will be able to use the brochure to simply compare the cross-sections and arrive at the safest, most efficient, and most cost-effective choice for a particular situation. The project team will also produce a detailed research report.
The primary objectives of the research study are to: Develop a collision model validated with NC data for sections of four-lane-with-median and five-lane highways between signals. Identify the operational impacts of u-turns on a divided four-lane highway.