Estimating the Safety Benefits of Red Light Cameras at Signalized Intersections in Urban Areas Case Study: The City of Virginia Beach

The Highway Safety Manual [HSM, 2010] recommends safety evaluations be performed before implementing any roadway treatment to predict the expected safety consequences. Safety consequences can be measured using crash prediction models, Crash Modification Factor (CMFs), or both. This paper develops a CMF to show the expected impact of red-light cameras (RLCs) on safety at signalized intersections. A CMF is a multiplicative factor used to compute the expected number of crashes after implementing a given countermeasure at a specific roadway site. RLCs are intended to improve driver’s alertness to avoid causing accidents. This paper analyzes accident data reported at thirteen signalized intersections in Virginia Beach in 2008 before the RLCs were installed and 2010 after the RLCs were installed. Safety performance functions (SPFs) and the empirical Bayes (EB) before-after methodologies are used to develop a CMF for this countermeasure. The result shows an overall CMF of 0.846, which is a 15.4% safety improvement. This result is not absolute; however, but sets a starting point for further investigations and potential inclusion in the future editions of the HSM.