SickKids study finds speed limit reduction made Toronto roads safer for pedestrians
A unique study design by SickKids researchers is one of few in the world to compare effects of speed limit reduction before and after implementation.
Researchers from The Hospital for Sick Children (SickKids) have shown lowering the speed limit from 40 km/h to 30 km/h on local Toronto roadways had a significant impact on the rate of pedestrian motor vehicle collisions (PMVC). Not only did the change reduce the number of PMVC, it also reduced injury severity for the pedestrians who were involved in collisions.
The research team says their work, published February 9, 2020, in BMC Public Health, adds strong support for speed reduction as a mechanism for reducing PMVC in Toronto and elsewhere.
“When a car is travelling at a higher speed, there are a host of factors that can increase the likelihood for a collision. Drivers have to contend with a reduced field of vision, shorter reaction time and increased stopping distance. Pedestrians also have increased difficulty making effective decisions about safe road crossings,” says Dr. Liraz Fridman, lead author of the study and former Postdoctoral Fellow in the Child Health Evaluative Sciences program at SickKids.
“Given there is potential for wide-ranging impact of speed limit reductions, we wanted to see how a reduction translated into the number of collisions and their effects on pedestrian injuries.”
Previous literature has shown the risk of pedestrian fatality as a result of a motor vehicle collision can be directly influenced by motor vehicle speed and the frequency of PMVC typically declines with speed reductions. However, studies on speed limit reductions have been largely observational, meaning it can be difficult to determine whether declines in PMVC rates are due to speed reductions or other causes.
SickKids researchers were presented with a unique opportunity when the City of Toronto reduced the posted speed limit from 40 km/h to 30 km/h on a number of local roads between January 2015 and December 2016. The team decided to look at the impact this implementation had on the rate of PMVC and pedestrian injury severity by comparing these rates before and after the implementation. They also compared these rates between the roads that received the intervention and those local roads which remained at 40 km/h elsewhere in the city. The study did not measure vehicle speed.
The researchers looked at a total of 10,624 PMVC that were reported in the City of Toronto from January 2013 to December 2018. They found a 28 per cent decrease in the PMVC rate and a 67 per cent decrease in fatalities and major injuries on the roads with a reduced speed limit after implementation. In comparison, roads with unchanged 40 km/h speed limits did not have any significant reduction in PMVC rates.
“In line with previous research, our results show systemic speed reduction typically has two results: A reduction of motor vehicle collisions and a higher probability of pedestrian survival should a collision occur,” says Dr. Andrew Howard, principal investigator of the study, Head of Orthopaedic Surgery and Senior Scientist, Child Health Evaluative Sciences at SickKids. “What speed reduction does not have to cause is increased travel times. We know traffic congestion is influenced much more by the amount of time spent at a standstill rather than the maximum speed a vehicle is able to reach.”
The researchers say their findings may be a conservative estimate of the effects of speed limit reduction as they were unable to access information about pedestrian traffic before and after the implementation. “With reduced vehicle speeds, it stands to reason we may see more pedestrians on the road. Therefore, the positive impact of speed reductions on safety may actually be much higher than what we found,” explains Howard, who is also a Professor in the Departments of Surgery and Health Policy, Management and Evaluation at the University of Toronto.
Future research may include the evaluation of speed limit reductions on major or arterial roads.
The funders for this study include the Canadian Institutes for Health Research (CIHR), the Pediatric Orthopaedic Society of North America (POSNA) Huene Award and SickKids Foundation.