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Abstract
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OBJECTIVE: Drivers with peripheral visual field loss (VFL) have been shown to have difficulty with some driving tasks, including maintaining speed and lane position and identifying potential hazards originating in the periphery. Previous studies have provided some evidence that drivers with VFL tend to compensate for limitations in their peripheral fields. The objective of this study was to examine the feasibility of using the National Advanced Driving Simulator (NADS) to evaluate differences in simulated driving performance in participants with VFL and those with normal peripheral vision.
METHODS: Sixteen participants, 6 with horizontal visual fields of less than 100 degrees and 10 control participants with normal visual fields, completed a 12 minute simulated drive in the National Advanced Driving Simulator (NADS). The simulated drive included straight and curved sections of rural highways, lead vehicle braking events, merging on and off a freeway and an intersection incursion. The simulator collected driving measures and a FaceLab 4.0 system recorded drivers' eye movements.
RESULTS: The VFL and comparison group performed similarly on most driving performance measures examined. The VFL group showed significantly greater lane position variability, particularly during the latter part of the drive. This was particularly evident on curves, during merges on and off the freeway and during the final lead-vehicle braking event. Later in the drive, participants encountered a hazardous event originating in the driver's peripheral field: a vehicle on an intersecting roadway failed to stop at a stop sign. Ten participants responded by coming to a stop and six steered around the incurring vehicle. On average, the VFL group took longer to release the accelerator in response to the incurring vehicle. Among those who stopped, the VFL group had a smaller time to collision indicating a smaller safety margin. Both groups exhibited similar maintenance of speed throughout the drive; however, the VFL group members made significantly longer glances toward the instrument panel, possibly to monitor their speed.
CONCLUSIONS: Participants with VFL showed greater variability in lane position and a delay in responding to an unexpected event during the simulated drive. The VFL group exhibited greater lane position variability during the final lead-vehicle braking event, which may indicate that they used a steering strategy to avoid the hazard. Given these drivers' potentially limited awareness of vehicles in the adjacent lane, this could be a risky choice. Devices such as blind spot and lane departure warnings might improve the safety of drivers with VFL, and moving the speedometer to a position closer to the windshield might facilitate all drivers' ability to monitor vehicle speed by reducing the magnitude and duration of downward glances. Overall, the results support the use of a motion-based simulator to evaluate driving performance in those with VFL in a safe, controlled environment. |