Abstract

The purpose of the present study was to investigate the effects of drivers' eye-level from ground and cognitive load on their driving speed control and information processing through driving simulation. In Experiment 1, the effects of drivers' eye-level and road complexity on driving speed when no speedometer was available, free recall performance, and subjective elapsed time estimation were examined. In Experiment 2, the relationship between the drivers' eye-level and cognitive load was investigated when their attention was systematically divided with regard to two different modalities of information processing (visual vs. auditory) and levels of task difficulty (complex vs. simple). The results of the two experiments showed that (1) the drivers who were test at a higher eye-level condition (6-feet) showed significant tendencies towards faster driving speed, greater free recall ability, and lower estimates of elapsed time than those who were tested at a lower eye-level condition (4-feet), and (2) consistent with previous studies, environmental factor such as road complexity proved to be very important in controlling driving speed: the subjects drove significantly slower in the complex road condition than in the simple road condition. In particular, (3) the effect of drivers eye-level on driving speed was homogeneous at various levels of target driving speeds (35, 45, 55, and 65 mph), and the subjects showed slower driving speed and worse information processing performance when their attention was divided by visual or complex distracters than by auditory or simple distracters. Based on the previous studies in this field which showed negative relationship between cognitive load and driving speed or free recall performance, but positive relationship between cognitive load and subjective time estimates, the drives' faster driving speed, greater free recall ability, and lower elapsed time estimates at a higher eye-level condition than those at a lower eye-level condition in the present study suggested the effect of driver's different levels of eye-height which is generally assumed to be a perceptual factor also can affect driver's cognitive factors.