Driver Gear-Shifting Behaviors and Errors

Survey data have revealed that forgetting the current gear is a frequent driver error (Reason et al., 1990), yet very little research has been done on how drivers move gearshift levers and what causes them to make gearshift errors. In two experiments, 65 adults of all ages drove two vehicles on a closed course. Participants each performed multiple trials in which they drove or reversed to a location, shifted to Park, and exited and re-entered the vehicle. For approximately 1000 shifts into Park, the movements and forces that drivers applied to the gearshift lever were measured. Data revealed that drivers shifted to Park in a ballistic manner, and continued to apply force to the gearshift lever after reaching the Park detent. This force far exceeded that which was required to move the lever into Park. On select trials, participants were induced to hurry, and distractions such as cell phones, radio, and conversation, were introduced during the driving task. A total of 35 gearshift errors (e.g., failure to shift, or mis-shift) were observed in both experiments, all but one of which occurred on either a hurried or a hurried-plus-distraction trial. On no trial did any participant leave the gearshift lever between Reverse and Park. Data suggest that participants rely on the kinesthetic feedback from the lever hitting the mechanical stop at the end of the Park gate to determine when they have reached the Park position, and that drivers are more likely to make gearshift errors when they are hurried or distracted.