Mechanisms of Automatic Transmission Console Shift Selection and Driver Egress 2009-01-0094

Inadvertent vehicle movement incidents, in which a vehicle rolls away after the driver has exited, may occur in automatic transmission vehicles as a result of environmental, vehicular, and/or driver factors. Some explanations have focused on claimed potential malfunctions or design flaws in the vehicle's console shift mechanism or in the automatic transmission itself. However, growing evidence suggests that driver errors unrelated to vehicle design may in fact be the primary cause of many inadvertent vehicle movement incidents. The present research extends previous work on driver gear-shifting behaviors and vehicle egress by conducting more in-depth analyses of data collected by Harley et al. (2008). First, timing characteristics of shifts into Park measured under hurried conditions were not affected by the presence of driver distraction, further evidence that gear shifting is not a visually-guided process, but rather a ballistic movement that is preplanned and, once initiated, cannot be modified or terminated until the planned action has been completed. Second, a noteworthy mode of vehicle exit reported by Harley et al. (2008) wherein the driver's foot remains on the brake during egress, was found to be associated with rapid vehicle exit times. Such egress patterns may combine with other driver errors (e.g., failure to shift into Park, failure to set the parking brake, and failure to remove the key from the ignition before exiting the vehicle) to allow inadvertent vehicle movements in which the driver is unable to safely regain control of the vehicle.