Are directional or non-directional hazard warnings more helpful for drivers with homonymous visual field loss?

People with homonymous visual field loss (HVFL), the loss of vision in the same half of the visual field in both eyes, are permitted to drive in some jurisdictions. However, the HVFL may cause delayed responses to hazards from the side of their vision loss (blind side). Warnings that indicate hazard direction may be beneficial. This study compared the effects of directional and nondirectional vibrotactile warnings on gaze behaviors and driving responses to pedestrian hazards in a driving simulator. Directional warnings consisted of vibrations on either the left or right side of the seat cushion to indicate the direction of an approaching hazard, while nondirectional warnings provided vibrations on both sides. Warnings were triggered at a 3-s time-to-collision, allowing HVFL drivers time to react. Both warning types were equally efficacious in reducing blind side collisions, with no difference in hazard brake response times. However, differences in gaze fixation behaviors suggest that participants with HVFL used the directional information, as they self-reported, to guide their gaze toward hazards on the blind side. Directional warnings were strongly preferred and resulted in quicker fixations on hazards.