Limits of spatial attention in three-dimensional space and dual-task driving performance

The present study examined the limits of spatial attention while performing two driving relevant tasks that varied in depth. The first task was to maintain a fixed headway distance behind a lead vehicle that varied speed. The second task was to detect a light-change target in an array of lights located above the roadway. In Experiment 1 the light detection task required drivers to encode color and location. The results indicated that reaction time to detect a light-change target increased and accuracy decreased as a function of the horizontal location of the light-change target and as a function of the distance from the driver. In a second experiment the light change task was changed to a singleton search (detect the onset of a yellow light) and the workload of the car following task was systematically varied. The results of Experiment 2 indicated that RT increased as a function of task workload, the 2D position of the light-change target and the distance of the light-change target. A multiple regression analysis indicated that the effect of distance on light detection performance was not due to changes in the projected size of the light target. In Experiment 3 we found that the distance effect in detecting a light change could not be explained by the location of eye fixations. The results demonstrate that when drivers attend to a roadway scene attention is limited in three-dimensional space. These results have important implications for developing tests for assessing crash risk among drivers as well as the design of in vehicle technologies such as head-up displays.

Research highlights▶ The present study demonstrates that drivers are unable to process all information present in the driving scene. ▶ Driving information that is further away from the driver is processed less efficiently than information closer to the driver. ▶ Increasing workload of the driver reduces the driver's ability to process information at different distances. ▶ Current assessments of spatial attention for driving safety (e.g., useful field of view) cannot account for these results. ▶ These results suggest that although the driver may be looking in a particular direction they are not processing all the information present in that region of the driving scene. ▶ These findings have important implications for the design of automotive head-up displays as well as tests designed to assess crash risk.