Results:Speed limit reductions from 40 km/h to 30 km/h were associated with a 28% decrease in the PMVC incidencerate in the City of Toronto (IRR = 0.72, 95% CI: 0.58–0.89). A non-significant 7% decrease in PMVC incidence rates wereobserved on comparator streets that remained at 40 km/h speed limits (IRR = 0.93, 95% CI: 0.70–1.25). Speed limitreduction also influenced injury severity, with a significant 67% decrease in major and fatal injuries in the postintervention period on streets with speed limit reductions (IRR = 0.33, 95% CI: 0.13–0.85) compared with a 31% notstatistically significant decrease in major and fatal injuries on comparator streets (IRR = 0.69, 95% CI: 0.37–1.31). Theinteraction term for group and pre-post comparisons was not statistically significant (p= 0.14) indicating that there wasno evidence to suggest a pre-post difference in IRRs between the intervention and comparator streets.

Conclusions:Declines in the rate of PMVC were observed on roads with posted speed limit reductions from 40 km/hto 30 km/h, although this effect was not statistically greater than reductions on comparator streets.