Abstract
This project updated and deployed a freeway safety performance measurement tool, building upon a previous project that developed the core methodology. The tool evaluates the cumulative risk over time of an accident or a particular kind of accident. The probability is estimated using a model that takes as input only variables that are derived from common inductive loop detectors. The estimated models predict increased risk of any accident occurring, as well as a number of characteristics of those accidents. By using this safety performance measurement tool, Caltrans will be able to evaluate the safety impacts of roadway changes over time. Specifically, it is anticipated that new deployments of intelligent transportation systems elements can be evaluated for their safety impacts by comparing the net risk of different kinds of accidents before and after deployment. The model predictions are best used to evaluate the cumulative probability of accidents and accident characteristics over longer time horizons and extended stretches of roadway.