Improving the safety relevance of front crash prevention testing programs: an examination of common characteristics in police-reported rear-end crashes

Kidd, David G.
Traffic Injury Prevention
In press

Objective: Front crash prevention (FCP) systems help prevent rear-end crashes, but the benefits may be limited if the systems are stymied by common crash circumstances or only target scenarios evaluated in vehicle testing programs. This study examined the prevalence of characteristics that may limit FCP system performance in police-reported rear-end crashes and the relevance of scenarios used to evaluate these systems.
Method: A total of 6,731,215 police-reported rear-end crashes from the Crash Report Sampling System and 4,285 fatal rear-end crashes from the Fatality Analysis Reporting System during 2016-2019 were analyzed. Percentages of police-reported rear-end crashes, nonfatal-injury rear-end crashes, and fatal rear-end crashes were computed for different crash characteristics. Roadway speed limit was used as a proxy for striking vehicle speed.
Results: Past research indicates that FCP systems are less effective when a striking vehicle is turning; when a struck vehicle is turning, changing lanes, or is not a passenger vehicle; in wintery weather; on wet or icy roads; or when the speed limit is 70 mph or higher. At least one of these characteristics was present in 14% of the rear-end crashes studied. A medium or heavy truck was struck in 32% of fatal rear-end crashes, and a motorcycle struck in 11%. Only 3% of rear-end crashes, 3% of nonfatal-injury rear-end crashes, and 1% of fatal rear-end crashes involved a straight-moving vehicle striking a stopped or decelerating vehicle on roads with a speed limit of 25 mph, which represents current scenarios used to evaluate FCP systems. In contrast, 36% of all rear-end crashes, 36% of nonfatal-injury rear-end crashes, and 11% of fatal rear-end crashes involved a straight-moving vehicle striking a stopped or decelerating vehicle on roads with a speed limit between 35 and 45 mph.
Conclusion: Circumstances shown to diminish FCP effectiveness accounted for a small proportion of rear-end crashes, and scenarios currently used to evaluate FCP systems accounted for an even smaller proportion. Evaluating FCP systems at speeds up to 45 mph will make FCP evaluations more representative of rear-end crashes. Incorporating a motorcycle or medium/heavy truck target would make evaluations more representative of fatal rear-end crashes.