Reducing Fatalities and Severe Injuries on Florida's High-Speed Multi-Lane Arterial Corridors. Part IV: Safety Improvements on Multilane Arterials in Florida: A Before and After Evaluation

摘要

This study examines the safety effects of the improvements made on multi-lane arterials. The improvements were divided into two categories: (1) corridor level improvements, and (2) intersection improvements. Empirical Bayes method, which is one of the most accepted approaches for conducting before-after evaluations, has been used to assess the safety effects of the improvement projects. The Safety Performance Functions (SPFs) used in this study are negative binomial crash frequency models that use the information on average daily traffic (adt), length of the segments, speed limit, and number of lanes for corridors. For intersections, the explanatory variables used are adt, number of lanes, speed limit on major road, and number of lanes on the minor road. The results of the analysis show that the resulting changes in safety following corridor level improvements vary widely. The overall effectiveness of each improvement type was positive in terms of reducing total, severe and rear-end crashes, except for roadway resurfacing projects, where the total number of crashes slightly increased. In all it can be concluded that FDOT is doing a good job in selecting the sites for treatment and it is very successful in improving the safety of the sections being treated although the main objective(s) of the treatments are not necessarily safety related.