This paper evaluates the impact of the Signal Head Upgrade Program in the City of Surrey,which was implemented by the Insurance Corporation of British Columbia (ICBC). To investigatethe impact of the program, Full Bayes multivariate linear intervention models with a multipleregression links representing time, treatment, and interaction effects as well as the trafficvolumes effects is proposed. The models were utilized to determine the safety impacts of theprogram on each combination of collision severity and collision time of occurrence (i.e.severe/day-time, severeight-time, PDO/day-time, PDOight-time) in the City of Surrey. Theresults indicated the effectiveness of the program in improving the safety of the treatedintersections as there were reductions in all types of collisions at the treated sites after theimprovement. However, such reductions were significant only for night-time severe collisionsand day-time PDO collisions.
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