Safety benefits of pedestrian crash avoidance systems

By Logan Dredske
Autonomous vehicle technology has been touted as a boon to safety, avoiding or mitigating the majority of crashes that are due to human error. Now a new report attempts to put numbers to how many pedestrian crashes could have been avoided or mitigated, and the value of avoidance.
In 2012 the U.S. saw about 4,800 pedestrian fatalities involving traffic crashes; on average, a pedestrian was killed every two hours and injured every seven minutes in traffic crashes. In 2015, fatality numbers rose to 5,376 deaths. As the frequency of traffic fatalities overall has decreased over the last 10 years, the proportion of those fatalities that are pedestrians continues to slowly increase (Figure 1). With the emergence of autonomous vehicle technology, how will these numbers be impacted?The Volpe National Transportation Systems Center, in support of the National Highway Traffic Safety Administration, developed and tested a methodology to estimate potential safety benefits of pedestrian crash avoidance/mitigation (PCAM) systems. PCAM systems are installed on vehicles and use detection technologies to prevent collisions with pedestrians by warning drivers, warning pedestrians, braking the vehicle, and/or steering the vehicle. Volpe utilized two national crash databases to gather historic crash data from 2011 to 2012. Under computer-simulated conditions, Volpe tested three different manufacturer’s PCAM systems to determine if they would have aided the vehicles enough to avoid or mitigate the crash.
Volpe’s simulations focused on two types of vehicle-pedestrian crashes: 1) a vehicle going straight and a pedestrian crossing in front of it, 2) a vehicle going straight and a pedestrian walking with/against the traffic, or standing in/adjacent to the road. When pedestrians crossed in front of the vehicle, PCAM systems avoided 7 to 77 percent of crashes using automatic emergency breaks (AEB). When pedestrians were walking along traffic or standing next to the roadway, 27 to 86 percent of crashes were avoided using AEB. The wide range of system effectiveness values was due to variations caused by technology differences in each manufacturer’s PCAM systems, in addition to differences among the two databases of historical crashes. On average, the simulations revealed that the PCAM systems avoided an average of 37 percent of crashes where a pedestrian crossed in front of the vehicle and 57 percent of crashes with pedestrians on the roadside.
Based on successful crash avoidances during simulations, the report estimates that from 2011 to 2012, PCAM systems would have saved up to $8.236 billion in comprehensive costs, including 901 lives valued at $9.146 million each. In addition, these statistics only include crashes that were avoided, and significantly rise when crashes that were mitigated are included.
PCAM systems research will play a vital role in the future as more autonomous vehicles enter our roadways. The ability of researchers to improve such technologies will increase with new vehicle crash reporting regulations by NHTSA that set future crash reporting guidelines for law enforcement and other authorities.
Logan Dredske is a Project Assistant at SSTI.