Abstract
Purpose :
Engaging in visual-manual secondary driving tasks (SDTs), such as adjusting infotainment controls, poses distraction risks that may impact the safety of drivers with impaired vision like homonymous hemianopia (HH). Rear-end collisions are the most common type of road crashes, and forward collision warnings (FCW) have proven effective in reducing such incidents. We conducted a pilot study to evaluate the impact of a visual-manual SDT on driving safety and the potential of FCW to mitigate negative effects of SDT engagement. We expected more pronounced effects of the SDT and the FCW on drivers with HH than drivers with normal vision (NV).
Methods :
7 participants with left HH (M = 49y; SD = 17y) with prior driving experience and 9 current drivers with NV (M = 44y; SD = 14.4y) completed 4 urban drives in a driving simulator. They encountered 6 rear-end crash scenarios in each drive where the car in front suddenly braked, 3 with SDTs and 3 without. 2 of the drives were with FCWs and 2 without. The SDTs were text messages requiring a response, displayed on an Android tablet, mounted to the right of the steering wheel.
Results :
Driving with an SDT increased the time to fixate on the front car (p < .001) and time to brake to avoid a collision (p<.001). For subjects with HH the negative effects of the SDT were exacerbated for time to brake (p=.04) and the minimum time to collision (p=.005). The minimum time to collision of the HH group (M=1.1s) was less safe than the NV group (M=1.5s). For the HH group, SDTs decreased the minimum time to collision further by 0.3s (p=.005), which was mitigated by the FCW, increasing the minimum time to collision by 0.4s (p=.01). An SDT doubled the frequency of lane crossings into the oncoming lane (15% to 30%) and caused 10 collisions for subjects with HH. While the FCW was effective in reducing collisions from 9 to 1, the frequency of lane crossings did not change (31% without, 29% with FCW) when an SDT was given.
Conclusions :
Visual-manual SDTs significantly reduced driving safety for all drivers with more pronounced effects for those with HH. FCWs effectively improved safety by increasing the minimum time to collision and reducing the number of collisions due to the SDT for drivers with HH but could not reduce the frequency of lane crossings when engaged in an SDT.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.