With Motion Perception, Good Visual Acuity May Not Be Necessary for Driving Hazard Detection

PURPOSE: To investigate the roles of motion perception and visual acuity in driving hazard detection. METHODS: Detection of driving hazard was tested based on video and still-frames of real-world road scenes. In the experiment using videos, 20 normally sighted participants were tested under four conditions: with or without motion interruption by interframe mask, and with or without simulated low visual acuity (20/120 on average) by using a diffusing filter. Videos were down-sampled to 2.5 Hz, to allow the addition of motion interrupting masks between the frames to maintain video durations. In addition, single still frames extracted from the videos were shown in random order to eight normally sighted participants, who judged whether the frames were during ongoing hazards, with or without the diffuser. Sensitivity index d-prime (d′) was compared between unmasked motion (n = 20) and still frame conditions (n = 8). RESULTS: In the experiment using videos, there was a significant reduction in a combined performance score (taking account of reaction time and detection rate) when the motion was disrupted (P = 0.016). The diffuser did not affect the scores (P = 0.419). The score reduction was mostly due to a decrease in the detection rate (P = 0.002), not the response time (P = 0.148). The d′ of participants significantly decreased (P < 0.001) from 2.24 with unmasked videos to 0.68 with still frames. Low visual acuity also had a significant effect on the d′ (P = 0.004), but the change was relatively small, from 2.03 without to 1.56 with the diffuser. CONCLUSIONS: Motion perception plays a more important role than visual acuity for detecting driving hazards. TRANSLATIONAL RELEVANCE: Motion perception may be a relevant criterion for fitness to drive.