To identify the characteristics of driver’s visual perception and measure the mental workload at different random hazard points on prairie highway, an on-road study was conducted with 28 drivers. The I view X HED eye tracker and MP150 multichannel physiological recorder were used to collect the driver’s eye movement and ECG data at different hazard scenarios synchronously. The gaze transfer theory and statistical methods were used to make comparative analysis of typical visual and mental workload evaluation indicators of drivers at different random risk points. The results show that no matter what kind of random risk is confronted, the percentage of drivers’ fixation duration to the current lane drops, where random risk belongs to increase. The distribution of eye glance transition proportions shows that drivers highly bias their scanning attention by only focusing on transferring between forward and the areas where the random belongs to. Compared with off-road risk points, the driver’s gaze transfer is more frequent when facing on-road risk points, and the gaze transfer path is fixed, indicating that on-road risks have higher requirements for drivers’ perception and greater information processing load. There are obvious differences in the degree of influence of the types of random risk points on driver’s psychology. The heart rate growth rate is the largest when drivers were confronted with overtaking cut-in (37.9%) and forward parking (38%), whereas the index RMSSD changes in the opposite way. It reaches the minimum value when the random risks are overtaking cut-in (22.679 ms) and forward parking (22.907 ms). Meanwhile, the driving speed shows larger fluctuation at risk points on the road. This study reveals that on-road hazards pose greater threats to drivers, and it can contribute to a better understanding of the potential hazards on the prairie highways and provide suggestions for future application of advanced driver assistance systems which can warn drivers about potential hazards.

Highway intersections are crash prone locations, and drivers' improper attention allocation and sudden increase of mental workload are main contributing factors. To explore the visual scanning characteristics and mental workload of drivers at prairie highway intersections with different characteristics, an on-road driving test was taken at 6 intersections scattered on a typical prairie highway with 3 different shapes and 2 different priority rules, and drivers' eye movement and ECG data were collected. The results show that there is significant difference in fixation allocation and transferring among intersections with different shapes and priority rules. The X-shaped intersection without the right of way shows the longest average fixation duration and the most gaze shifts between the drivers' lane and the intersection road, whereas the three-way intersection with the right of way shows the shortest fixation duration and the gaze transfer path is relatively simple and the transfers are less. The mental workload implies almost the same conclusion, with the X-shaped intersection without right of way shows the highest mental workload which is manifested by largest heart rate growth rate and the lowest RMSSD, whereas the three-way with priority of way shows the opposite trend. This study revealed that both intersection types and priority rule made differences in drivers' scanning behavior and mental workload at prairie highway intersections, which can support the development of appropriate countermeasures regarding the applications in advanced driver assistance systems and the design of intersection constructions to warn drivers about potential critical events at different types of intersections.