Estimating Pedestrian Fatal Crash Risk

Pedestrians are highly vulnerable in traffic with the young, aged and alcohol-affected being at even
greater risk. Vehicle speeds are the primary determinant of pedestrian crash risk and, more
importantly, injury severity in the event of a crash. Scientifically-based, well-established mathematical
relationships exist for vehicle stopping distance, as a function of the initial travel speed, and the risk of
death to a pedestrian, given the vehicle impact speed. The main purpose of the research was to build on
current research evidence concerning the risk of death to a pedestrian, as a function of impact speed, in
order to develop a reliable method for estimating the relative risk of a fatal crash involving a
pedestrian, as a function of alternative travel speed choices. These estimates apply to a pedestrian in
the path of two vehicles travelling at different initial speeds and, within meaningful limits, enable pair-
wise comparison of risk for selected initial travel speeds. The model outputs offer objective new
information on pedestrian fatal crash risk, based on the laws of kinematics and the biomechanical
limits of humans exposed to kinetic energy. By allowing differences in travel speed choices to be
translated to changes in pedestrian fatal crash risk, key groups, such as drivers and riders, pedestrians,
stakeholders, policy makers, and traffic and road engineers, can be provided with scientifically-derived
information on the role of speed. Proposed future developments of the model are also discussed.