Influence of Travelling Speed on the Risk of Injury Accident: a Matched Case-Control Study

This matched case-control study deals with the effect of the individual travelling speed on the risk of involvement in a road accident. The cases were cars involved in injury accidents dealt with within the framework of an in-depth accident investigation programme. The matched controls were cars passing the same road site as the crash-involved car, in the same conditions but without being involved in an accident. Only normal weather, daytime and free-flow conditions were considered. Overall, 52 cases and 817 controls were used. The speeds were obtained from kinematic reconstructions for the crash-involved cars, and using a laser speed gun for the controls. A significant positive relationship is found between the individual travelling speed and the risk of injury accident. Nevertheless, this study has limitations, due to the relatively small number of cases and to the data used (kinematic reconstructions always involve some degree of interpretation)

Assessing the Safety Implication of Alternative Speed Limits in California

UC-ITS-2019-11This project combined the statewide crash data (SWIRTS) and traffic data (PeMS) to develop statistical models to determine the safety impacts of alternative speed limits on California highways. The models examined whether various factors about crashes, including average traffic speed and truck-involvement, correlated with outcomes such as crash severity. The models were then used to test the impact of four alternative speed limit policies (B-E) on the predicted number of fatal crashes and unsafe-speed related crashes in urban and rural areas. The policies were: (A) Existing differential speed policy for cars (65 mph) and trucks (55 mph); (B) Raising the speed limit on interstates for trucks from 55 to 65 mph; (C) Raising the speed limit on interstates from 55 to 75 mph for trucks and 65 to 75 mph for cars; (D) Lowering the existing differential speed on interstates from 55 to 50 mph for trucks and 65 to 60 mph for cars; (E) Raising the existing differential speed on interstates from 55 to 70 mph for trucks and 65 to 80 mph for cars. The policy analysis shows a difference in the predicted number of crashes (fatal, unsafe speed) in and between urban and rural areas. The percentage increase/decrease in predicted fatal crashes in rural areas is lower than urban areas across all policy alternatives