Controlled studies identified several factors that influence drivers' swerving when responding to in an emergency situation. Specifically, driver age, time-to-contact, amplitude of the steering action (steer within lane or swerving into the next lane), distraction, fatigue, natural lighting and available buffer space were identified as factors that influence steering behaviors. The goal of the current research was to identify the extent to which each factor changed swerving performances of drivers who were faced with a crash or near crash. Results from crashes and near crashes were obtained from the InSight (SHRP-2) naturalistic driving study.
The results from the controlled studies and the results from the naturalistic driving research were consistent in many ways. Drivers engaged in a visual-manual secondary task were much younger than were the drivers who had no distracting secondary task. Also, those who swerve at night were much younger (M = 22.1 years), than daytime (M = 36.8 years). Drivers engaged in a visual-manual secondary task, (typically younger drivers), were less likely to brake hard while swerving, presumably because they were already trying to do two things at once. Drivers with shorter times-to-contact steered out of their lanes faster, but also exhibited greater counter-steer which resulted in longer times for a complete lane change. Also, drivers over age 25 steered only 2 feet, while drivers younger than age 25 steered an average of over 6 feet regardless of rain or not. Steering responses associated with fatigue, as well as responding to slowing moving lead vehicles were also addressed.