A systematic review and meta-analysis of impact speed and probability of pedestrian fatality

Abstract

Background Pedestrians in motorized vehicle crashes constitute the largest group of traffic fatalities worldwide. Excessive speed is the primary contributory factor in crashes. The relationship between impact speed and the risk of pedestrian fatality has generated discussions concerning the safe speed for areas with high pedestrian traffic.

Methods Four electronic databases (MEDLINE, EMBASE, COMPENDEX, SCOPUS) were searched to identify relevant studies. Two authors independently assessed records retrieved in adherence to the PRISMA statement. The included studies reported data on pedestrian fatalities or injury severities from motorized vehicle crashes where the impact speed was known. Summary odds ratios (OR) were obtained using meta-regression models. Time trends and publication bias were assessed.

Results The following results are preliminary as the study is still ongoing. A total of 57 studies were collected for a full-text assessment, and 27 of them met inclusion criteria and 20 were included in the meta-analysis. Of these, 15 focused on fatal crashes and 5 focused on non-fatal crashes. These analyses found that when the impact speed is increased by 1 km/h, the odds for pedestrian fatality increases on average by 11%, (OR=1.11, 95% CI: 1.10 to 1.12). The risk of fatality reaches 5% at an impact speed of 28 km/h, 10% at 36 km/h, 50% at 57 km/h, 75% at 67 km/h and 90% at 78 km/h. Publication bias and time trend bias among included studies were found and assessed.

Conclusions Pedestrian fatality risk increased monotonically with impact speed, as well as the risk for AIS2+ and AIS3+ injuries. These results can help inform road safety policy makers regarding appropriate speed for areas of high pedestrian travel.