The objective of this study was to investigate the effects of driver distraction - both cognitive and visual - on reaction time to unexpected road hazards. Participants operated a driving simulator while intermittently answering prerecorded questions of various difficulty (holding a "conversation" with the computer), or dialling specified numbers into a cellular telephone. Two road hazards were presented at unpredictable times and locations, including red brake lights and a red pedestrian-shape of approximately the same area as the brake lights. Targets were presented in two different locations: directly in front of the driver at the bottom of the screen, and off to the side of the road. The results showed a significant overall increase in reaction time for older subjects, as well as a strong interaction with the dialling task condition. There were no significant differences from the control for either easy or difficult verbal response conditions. In addition, stimuli on the side of the road took significantly longer to respond to, especially when combined with the dialling task. These data suggest a strong link between age, visual task load, stimulus location, and increased reaction time to unexpected stimuli.
Abstract