Measuring Attentional Demand in a Virtual Environments Driving Simulator

Abstract

The measurement of drivers' attentional demand is of importance to highway designers as well as to human factors engineers concerned with in-vehicle navigational displays and their user interface. When attentional demand is great, older drivers in particular are subjected to information overload which may adversely affect their driving performance. In 1967, Senders, et. al. measured drivers' attentional demand using a visual occlusion device. They found that attentional demand increased with vehicle velocity, but their study was limited to off-road driving due to safety considerations. The present study focused on the establishment of baseline quantitative measures of attentional demand as a function of vehicle velocity, road curvature, and amount of oncoming traffic. Eight experienced drivers drove a virtual environments driving simulator while controlling the visibility of the forward scene via a foot switch. They were instructed to stay in their lane and obey all traffic regulations, while trying to keep the forward scene visible as little as possible. Attentional demand was calculated as the percent of time drivers viewed the forward scene during a run. While driving at 100 kph the average attentional demand (86%) was significantly higher (p < .01) then when driving at 33 kph (77%). The finding that an increase in vehicle velocity of 67 kph resulted in only a 9% increase in attentional demand was somewhat surprising. As expected, the attentional demand of drivers on curves (85%) was significantly higher (p < .05) then when driving on a straight road (81%). The effect of traffic versus no traffic on curves was also statistically significant. The attentional demand on curves with moderate on-coming traffic was 88% versus 80% when there was no traffic. This study demonstrated the feasibility of using a virtual environments simulator to measure drivers' attentional demand. Future research will study attentional demand using novice and older drivers.