Safety Comparison Of Roadway Design Elements On Urban Collectors With Access PDF Download

In order to develop performance measures to communicate the effect of Virginia's access management program, five tasks were performed: (1) the appropriate literature was reviewed, (2) a catalog of potential performance measures was developed, (3) potential users of the performance measures were surveyed, (4) promising measures were tested, and (5) measures were recommended. The literature review yielded a catalog of 42 potential performance measures. These measures are based on five goals and nine objectives related to the desired outcomes of the access management program. The five goals are reduce congestion, enhance safety, support economic development, reduce the need for new highways, and preserve the public investment in highways. Seven objectives are design elements: reduce conflict points, provide adequate distance between signals, provide adequate distance between unsignalized access points, add medians and two way left turn lanes, add dedicated turn lanes, restrict median openings, and use frontage roads and supporting streets. Two objectives are administrative elements: to enhance cooperation between agencies, and plan for future development. Professionals engaged in access management provided their views regarding aspects of performance measures. Performance measures that reflected improved safety, measures related to goals, and measures related to design elements were favored. The literature review and comments from VDOT staff and other professionals yielded 23 candidate measures that were tested for ease of data collection and computation. The results showed substantial variation in the time required to estimate each measure. Five criteria were used to determine performance measures for implementation: (1) Does VDOT control the measure? (2) Is improvement likely? (3) Is the measure an outcome, output, or input? (4) Does the survey support the measure? and (5) How much data collection effort is required? Each of the 23 measures was evaluated against the five criteria, and 7 measures were selected for review and refinement by the steering committee. Five performance measures were recommended for implementation: crashes per million vehicle miles traveled, percentage of signals with spacing at or above standard distance, percentage of commercial entrance permits issued that meet access management standards, percentage of median openings with left turn lanes, and percentage of localities with a corridor access management plan. Appendix A describes how each of the five measures may be computed.