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Abstract
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This paper presents findings of different experiments condicted to investigate: 1) the role of extra-foveal and foveal vision in the visual information acquisition process of the driver, and 2) the effect of driver's visual information acquisition behavior on his driving performance.
All the data obtained in the experiments were collected under actual highway driving situations by using an eye-marker camera system. The important results obtained from the experiments are as follows:
I. The drivers need not use foveal vision to maintain lane position and headway but can use peripheral (extra-foveal) vision for such tasks, but where speed of information processing is critical, drivers must resort to foveal vision.
a. The data obtained from experiments in open-road driving under normal situations suggest that a large portion of the information necessary for maintaining lane position and direction is obtained from extra-foveal vision.
b. Car-following tasks can be performed by extra-foveal vision. In one of the experiments it was shown that a driver could follow a lead car at 70 feet headway and at 70 mph by monitoring the lead car while maintaining fixations at 25° away from the longitudinal axis of the car.
II. While performing a control task in extra-foveal vision the performance of the driver in that task degrades with increase in eccentricity angle.
III. While performing two spatially separated control tasks, simultaneously, the driver's performance in foveally attended control task also degrades. The degradation in the performance of foveally attended control task increases with increase in angular separation between the two tasks.
IV. While performing two simultaneous tasks in driving the selection of driver's visual search and scan depends upon the following two decisions:
a. decision to voluntarily attend to information available in the extra-foveal vision.
b. decision to allocate available search and scan time between foveal and extra-foveal parts of the visual field in performing each task.
The lack of correlation of accidents to visual acuity (foveal) is not surprising when evidence of this and other related research suggest the dominant role of extra-foveal vision in driving. |