Evaluation of Rationally Implemented Speed Limits on Collector Roadways.

To address speed-related safety issues the U.S. Department of Transportation established a Speed Management Team which, in turn established an experimental projects related to the implementation and evaluation of rationally established speed limits. By definition, a rationally established speed limit is one that is based upon formal review and engineering study and is reflective of realistic roadway speeds, which are reasonable under normal travel conditions. An additional benefit expected with rationally determined speed limits is the establishment of a reasonable enforcement threshold for law enforcement personnel, and allows for strict, yet fair, enforcement of the speed limit. The specific goal of this project was to evaluate the Massachusetts rational speed limit demonstration project, which inaddition to the rational speed limits included a rigorous enforcement campaign as well as an intense public information and education (PI &E) campaign. For six project roadways implementation of the rational speed limit meant an increase of five mph along each roadway. Data from almost 1.5 million free flow vehicles was collected over a 20-month time frame and provided 85th, 95th, and mean speeds for each of 12 data collection locations.In general, the speed parameters tended to reduce by one to two mph during the enforcement period, and later increased during the post enforcement period. During the post-enforcement period, the 85th percentile speed increased, on average, 0.3mph. In some instances the speed remained constantthroughout all stages of the project, and in fewer instances, the speeds in the post enforcement period exceeded the initial baseline speed parameters. Based upon the information collected in pre and post opinion surveys, the community residents were aware of the project, the rational speed concept, and more importantly, they supported both the increase in speed andenforcement. Overall the project was considered to be a success by thoseinvolved based upon several of the documented findings and lessons learned.