Driver Workload and Visual Studies (0-5911-S)

The goal of this project was to gain a better understanding of driver performance at high speeds. Several study approaches were used including a closed-course study, simulator studies, and open-road studies where following distance and gaps at passing were measured. When drivers were responding to a vehicle slowing in their lane, the reaction time of drivers in the simulator study at the 85-mph speed was statistically longer than that of drivers at the 60-mph speed. Drivers took more time at the higher speed to respond to a lead vehicle slowing in their lane. The passing-gap study found that drivers passed more closely to the larger vehicle (recreational vehicle) than the smaller vehicle (sedan). Passing gap increases by 10 feet for each mile-per-hour increase in speed difference between the lead vehicle and the following vehicle. The faster a driver approaches a vehicle, the greater the passing-gap distance. Performance declines when a driver is multitasking at higher speeds. The simulator study showed that driving 85 mph required more mental effort than driving 60 mph, leaving less mental capacity free to do the arithmetic problems. Driving performance may decline even further in situations where drivers are engaging in other physically or mentally distracting tasks.