Abstract
Purpose :
Vision impairment (VI) and secondary task involvement may impact driving performance and cause safety concerns. Collision Warning Systems (CWS) can assist drivers in avoiding collisions. We investigated the effects of a CWS on driver workload and hazard responses when drivers with VI were occupied with audiobook secondary tasks in a simulator.
Methods :
To date, 10 subjects with VI (49–88y, median CS 1.4 log units) and 10 with normal vision (NV) (61–87y, median CS 1.95) participated. They completed 4 city drives in a counterbalanced order: baseline, with CWS, with audiobook task, with both audiobook task and CWS. There were 10 pedestrian hazards per drive that crossed the road from the left or right on a long straight road segment. The CWS gave a directional vibro-tactile warning of an approaching hazard when collision risk exceeded a pre-defined threshold. For drives with secondary tasks, subjects listened to an audiobook, repeated target words out loud, and answered comprehension questions at the end. After each drive, subjects completed a NASA Task Load Index survey to assess perceived workload.
Results :
VI subjects were slower to respond to hazards, had more collisions and triggered more CWS warnings than NV subjects (33 vs 22%). The audiobook task reduced the number of scans for both groups (p= 0.02). Collision rates were highest (6.7%) for the VI subjects when driving with the audiobook task without the CWS, but reduced to 0% when driving with the CWS. Overall, VI subjects perceived higher workload than NV subjects (p= 0.04). The audiobook task significantly increased overall workload for NV subjects (p< 0.001), but not for VI subjects because they perceived high workload even without the audiobook task. The CWS reduced workload for VI subjects when driving without the audiobook task, but slightly increased workload for both groups with the audiobook task. Both groups perceived the highest mental workload when driving with audiobook task only, and the highest effort and physical demand when driving with both audiobook task and CWS.
Conclusions :
When driving with an audiobook secondary task, the VI group had the highest collision rates, but collisions were greatly decreased with the support of the CWS. The VI group perceived higher workload than the NV group in general. The CWS decreased workload for VI subjects only when driving without the audiobook task.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.