Panel Discussion – Factors related to perceiving the relative speed of leading vehicles in high-speed rear-end crashes

Abstract

Forensic human factors practitioners are often engaged to offer expert opinions in cases involving rear-end collisions. Such collisions represent approximately 25% of all automobile crashes and have done so for many years. The sad fact is that people run into the backs of slow moving or stopped vehicles with a low, but persistent probability. According to the 100-car study, the probability is 1 in 1.84 million miles traveled (Americans drive a total of about 3 trillion miles per year). A number of researchers have examined the circumstantial and perceptual issues related to rear-end crashes in an effort to understand why drivers have such a difficult time perceiving the relative speed of leading vehicles. Results from these studies are often cited in expert reports and testimony. In particular, the “looming threshold” established in these studies is sometimes used to establish the expectation of braking or steering responses. However, when reconstruction data are used to calculate looming thresholds, the values are usually much higher than those obtained in controlled studies. It is unclear whether these data represent the same phenomenon. The purpose of this panel discussion is to examine the breadth of data related to rear-end crashes and offer insight into the discrepancy between reconstruction and experimental results.