Assessing the effectiveness of speed limit reduction in Edmonton: A case study analysis

This study evaluates the impact of reducing the default speed limit from 50 km/h to 40 km/h on traffic safety and drivers' behavior in Edmonton, Canada. The research comprehensively examines collision and speed data to assess the outcomes of the new speed limit. Collision data was analyzed across three distinct periods: pre-COVID (2017-2019), the COVID period (2019-2021), and the after-implementation period (August 2021 to July 2022). Speed surveys were conducted on 219 road segments before and after the implementation of the speed limit change. The study utilized a before-and-after with a comparison group approach to evaluate the impact on collisions, using 50 km/h roads that maintained their speed limit throughout as the comparison group. The impact of the reduced speed limit on road safety was assessed by analyzing collision data for two periods, pre-COVID (2017-2019) and COVID (2019-2021), compared to the period after setting the new speed limit (2021-2022). Two-sample t-tests were employed to examine the change in speeds. The analysis revealed statistically significant reductions in the overall number of collisions and injuries and fatalities resulting from collisions, by 25% and 31%, respectively. The study also categorized neighborhoods and roads to demonstrate the areas that experienced the greatest benefits. Speed data showed statistically significant reductions in the average and 85th percentile speeds, with drivers lowering their speeds at 115 locations, accounting for 53% of the surveyed locations. Moreover, higher speed reductions were observed on local roads compared to collector roads, and narrower roads compared to wider roads.. Overall, the study demonstrates that reducing the speed limit can lead to lower speeds and fewer collisions on the roads, creating a safer road environment for drivers, pedestrians, and cyclists. Additionally, it provides a detailed framework for municipalities to evaluate the effectiveness of their speed limit reduction programs.