Evaluating Safety Benefits of the Insurance Corporation of British Columbia Road Improvement Program Using a Full Bayes Approach

Abstract

The objective of this study was to conduct a time-series (before-to-after) evaluation of the safety performance of a sample of locations that have been improved under the Insurance Corporation of British Columbia (ICBC) Road Improvement Program. The program started in 1989 when ICBC established partnerships with local road authorities in British Columbia, Canada, and works cooperatively to make sound investments in road safety improvements. The overall effectiveness of the road improvement program was assessed by determining whether the frequency or severity of collisions at the improvement sites has been reduced after implementation of the improvement, and by quantifying the program costs versus the economic safety benefits to determine the return on ICBC’s road safety investment. Seventy-two urban intersections were included in the evaluation. The methodology adopted for estimating the safety benefits was a before–after study with the full Bayesian method, while the benefit–cost analysis was carried out by using two indicators: net present value and benefit–cost ratio (B/C) with a payback period of 5 years. Overall, the total reductions of severe (fatal plus injury) and nonsevere (property damage only) collision frequency for intersections with new pedestrian signal installations were found equal to −24.54% and −6.21%, respectively; −22.95% and −10.78%, respectively, for intersections with geometric design improvements; and −13.76% and −5.04%, respectively, for intersections with traffic signal upgrades. Finally, an overall B/C ratio of 4.32:1 was achieved.

Before–After Evaluation of Left-Turn Lane Extension Considering Injury Severity and Collision Type

“…Specifically, a comparison group of sites is used for correction of time trend effects, including history and maturation ( 11 ). A reference group is used for correction of the regression to the mean ( 27 ). More details about the EB before–after study can be found elsewhere ( 9, 26 ).…”

“…Moreover, the FB approach efficiently integrates the estimation of the collision prediction model and treatment effects in a single step, leading to a reduction in the data requirement ( 30, 32 ). Thus, advanced evaluation models such as intervention models could be developed with the FB technique ( 27, 28, 31, 34, 35 ).…”