Safety and Operational Performance Evaluation of Four Types of Exit Ramps on Florida's Freeways

摘要

This project mainly focuses on exit ramp performance analysis of safety and operations. In addition, issues of advance guide sign for exit ramp are also mentioned. Safety analysis evaluates safety performances of different exit ramps used in Florida and nationally. More specific, the research objectives include the following two parts: to evaluate the impacts of different exit ramp types on safety performance for freeway diverge areas; and to identify the different factors contributing to the crashes happening on the exit ramp sections. Operational analysis determines different ramp effects, and guidance for selecting optimal exit ramp type. Beside ramp type evaluation and selection, issues of ramp section and cross road section are also demonstrated. Minimum ramp length and minimum distance between ramp terminal and downstream/upstream intersections are calculated. For advance guide sign, placement distance models are presented respectively for the three different installation methods: ground sign installation, overhead sign installation, and median sign installation. All possible factors, such as freeway geometric design, traffic conditions, driver behavior, exit ramp type, and posted speed limits on freeway and ramp, are taken into consideration while modeling.