Abstract
In the past decade, there has been a rapid increase in reports of sudden unintended acceleration (SUA). While the precipitating conditions for SUA are well known, we know little about how drivers respond in such emergencies and how particular responses might lead to crashes. The goal of this study was to examine how drivers respond to a SUA in a controlled high-fidelity driving simulator experiment that closely replicated the motion cues of real driving. Younger and older drivers encountered a SUA event that mimicked a vehicle malfunction at the end of a simulated drive while executing a parking maneuver. A hierarchical cluster analysis revealed three distinct brake response patterns: hard braking, gradual braking combined with brake pumping, and light or no braking. The critical point in these brake responses, that is, the point at which response types diverged, was about 1 s after the onset of the SUA. Furthermore, older female drivers responded with less brake force than did younger or male drivers. These results indicate that over half of drivers react to SUA with indecisive responses that could lead to crashes. These results have important implications understanding how SUA may lead to crashes. The results also highlight the potential need for advanced driver assistance systems to aid drivers in hazard situations.