Driving with hemianopia VIII: Effects of a vibro-tactile assistance system on safety and gaze behavior in pedestrian crossing situations

People with homonymous visual field defects (HVFDs), the loss of vision in the same half of the visual field in both eyes, are permitted to drive in some jurisdictions. However, the HVFD may cause difficulties in detecting hazards approaching on the side of the field loss (the blind side). An advanced driver assistance system (ADAS) could assist with hazard detection, but little research has been conducted to evaluate the potential benefits of an ADAS for visually impaired drivers. We developed a prototype vibro-tactile assistance system for drivers with HVFDs and conducted a proof-of-concept driving simulation study to evaluate the system. Given that pedestrian accidents are the second most frequent cause of death in road traffic and most of those accidents occur in urban scenarios, we evaluated the potential of the assistance system to improve responses to pedestrian hazards in a city environment. Sixteen participants, of which eight had HVFDs and eight had normal vision, took part. Our analyses evaluated the effects of the driver assistance system, crossing direction and pedestrian behavior on the safety of pedestrian events and the participant's gaze behavior at each of the 256 crossing situations. Generalized linear mixed effects models were used to assess binomial outcome variables. Despite the limited sample size, the results suggest that the vibro-tactile directional warnings were effective in directing the drivers' gaze so that they were looking in the necessary direction before a potential hazard occurred. More time was spent fixating pedestrians on the blind side when the ADAS was engaged and as a result, the safety of street crossings from the blind side improved. The effect of the ADAS was greater on responses to pedestrians from the blind than the seeing side. With an activated ADAS, crossings from the participants' blind sides were as safe as from their seeing sides, and as safe as the crossings when normally-sighted participants were driving. The results suggest that the vibro-tactile ADAS is a promising approach to improve the safety of drivers with HVFD and surrounding traffic.