Safety Consequences of Flexibility in Highway Design

OBJECTIVE The objective ofthis project is to develop guidance to enable project planners and designers to estimate the safety consequences of varying geometric design values for highways through rural communities. TASKS PHASE I Task 1: Synthesize available information on the safety consequences of varying geometric design values on highways passing through rural communities. Task 2: Survey state departments of transportation and others to identify projects on highways through rural communities that demonstrate geometric design flexibility. The survey shall identify the geometric design elements where flexibility was used, why flexibility was used, and the availability and extent of before- and-after data. Task 3: Submit an interim report that summarizes the information from Tasks I and 2 regarding alignment, cross-section, and intersection geometric design elements such as: (a) lane and shoulder widths; (b) design speed; (c) horizontal and vertical alignment; (d) superelevation; (e) intersection sight distance; (f) median presence; (g) clear zone; (h) shoulder versus curb and gutter; (i) sidewalk width; and (j) intersection curb return radius. The interim report shall include a data collection and analysis plan to develop information to estimate the safety consequences of design variations for highways through rural communities. The interim report shall also outline the final format in which the information will be presented. Task 4: Meet in Washington, D.C., with the project panel to review the interim report approximately 1 month after its submittal. Submit a revised interim report reflecting the panel's review comments. PHASE II Task 5: Conduct the data collection and analysis as outlined in the approved work plan and develop the information in the format outlined in the interim report. Task 6: Submit a final report documenting the entire research effort. The final report shall describe how the project was conducted. The final report should include clear, practical guidance in a format suitable for incorporation into design and safety documents (e.g., "Green Book") and processes (e.g., Interactive Highway Safety Design Model) for resurfacing, restoration, rehabilitation, or reconstruction projects. The information should enable project planners and designers to estimate the safety implications of design decisions for specific projects. This information may be in the form of charts, tables, and estimation procedures.