Investigating Effects of Assistance Systems For Visually Impaired Drivers at Preventing Traffic Accidents

Abstract

Visual field defects (VFD) are closely associated with driver hazard perception. Drivers with advanced VFD are more likely to be involved in traffic accidents than healthy-sighted drivers even though they apply extra movements to overcome the defects. Given difficulties in dealing with particular situations, such as finding traffic signals, machinery assistance is necessary for improving driving safety. However, it has been less explored that which assistance systems would be helpful for visually impaired drivers in which traffic situations. To have a better understanding of driving with VFD and provide a safer traffic environment for drivers with advanced VFD, this study aimed to investigate effects of three driver assistance systems on reducing traffic accidents regarding several traffic situations. Methods:A driving simulator experiment using 66 healthy-sighted drivers generated advanced VFD on a screen for all simulations. This study designed a Baseline condition and three assistance systems based on time-to-collision (TTC) in hazardous events: automatic braking (AB; TTC = 0.8s) and giving voice guidance about driver behavior to cope with encountering situations. Two guidance systems were presented in different alert timings (VGEarly; TTC = 4s, VGLate; mean TTC = 2.81s). We classified 29 hazardous events into four categories: traffic signals, oncoming right-turning cars, objects that appear from driver’s right and left sides, then counted the number of traffic accidents. Results:Data provided that all assistance systems showed the lower number of accidents than the Baseline. Whereas drivers in the Baseline were not able to find traffic signals due to the defect, no accident cases related to the situation were observed in the assistance system conditions. When an oncoming car turned to the right, drivers in the VGEarly showed the lowest accident rate among all conditions. The AB led the great number of accidents in the oncoming car situation but yielded no accidents with hazards approaching from the right. Results showed that both VG systems were more likely to reduce the accidents with hazards from the left than the AB. More specifically, the VGEarly decreased the accident rate by approximately 15% more than the VGLate.Discussions:This study attempted to figure out which system is effective for visually impaired drivers in which traffic situation. Interestingly, the effect depended on situations. For example, the AB led no accidents when encountering objects from the right side unlike the VG systems. The VGLate had a potential of reducing accidents, but the VGEarly more contributed to reducing accidents rather than the VGLate. Because VFD led failure in driver perception that is a very initial stage of information processing, in general, VGEarly is considered to produce appropriate performance. The current study is limited to investigating accident rates, thus next study should perform further analyses of driver response that can provide two-way feedback between the system and the driver. Despite the limitation, the present study found that assistance timings and traffic situations are critical factors influencing system design for visually impaired drivers. Empirical findings are expected to provide insights into practical assistance designs for driving with VFD.