Impact Speed and a Pedestrian's Risk of Severe Injury or Death
Source: AAA Foundation for Traffic Safety
The relationship between impact speed and a pedestrian's risk of death has been studied extensively; however, past studies of data from the United States are now several decades old. Older studies of data from the United States may not be generalizable to the present situation because of changes in the composition of the walking population, vehicle design, and medical care over the past several decades. Similarly, the ability to generalize from recent European studies to the United States is unclear due to differences in the types and sizes of vehicles driven in Europe versus in the United States.
This study estimates of the risk of severe injury or death for pedestrians struck by vehicles in the United States using data from a federal study of crashes that occurred in the United States in years 1994 - 1998 in which a pedestrian was struck by a forward-moving car, light truck, van, or sport utility vehicle. The data were weighted to correct for oversampling of pedestrians who were severely injured or killed. Logistic regression was used to adjust for potential confounding related to pedestrian and vehicle characteristics. Risks were standardized to represent the average risk for a pedestrian struck by a car or light truck in the United States in years 2007 - 2009.
Results show that the average risk of severe injury for a pedestrian struck by a vehicle reaches 10% at an impact speed of 16 mph, 25% at 23 mph, 50% at 31 mph, 75% at 39 mph, and 90% at 46 mph. The average risk of death for a pedestrian reaches 10% at an impact speed of 23 mph, 25% at 32 mph, 50% at 42 mph, 75% at 50 mph, and 90% at 58 mph. Risks vary significantly by age. For example, the average risk of severe injury or death for a 70-year-old pedestrian struck by a car travelling at 25 mph is similar to the risk for a 30-year-old pedestrian struck at 35 mph.
These results could be used to inform efforts to improve pedestrian safety, for example, by limiting traffic speeds to levels that are unlikely to result in severe injury or death in places where pedestrians and vehicles may encounter one another, creating physical separation of pedestrians and vehicles in places where higher traffic speeds are desired, and developing vehicle-based systems that detect pedestrians and warn the driver or brake automatically when a collision is imminent.
