Increased visual and cognitive demands emphasize the importance of meeting visual needs at all distances while driving
DOI: 10.1371/journal.pone.0247254
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Summary
This study investigates the interaction between visual acuity and cognitive load in driving safety, addressing the lack of scientific justification for current static visual acuity standards. While legal thresholds exist for obtaining a driver’s license, it remains unclear how reduced vision impacts behavior when combined with high mental workload. The authors hypothesized that degraded visual acuity would negatively affect driving performance specifically under high cognitive demand, with greater impairment observed at lower acuity levels. The experiment utilized a high-fidelity driving simulator with 21 young adult participants who had normal or corrected-to-normal vision. Participants were divided into two groups based on induced visual degradation using contact lenses: a "lower degradation" group reduced to 6/15 (the legal threshold in Québec, Canada) and a "higher degradation" group reduced to 6/75. Each participant completed two scenarios in both optimal and degraded vision conditions. The rural scenario involved single-task driving with pre-programmed hazards, representing lower cognitive load. The highway scenario required simultaneous driving and a secondary visual search task on a navigation device, inducing higher cognitive load. Driving behavior was assessed using metrics including mean speed, speed variability, and standard deviation of lateral position (SDLP). The results supported the hypothesis that visual quality degradation impacts driving behavior only when combined with high mental workload. A dual-task effect was observed, provoking less stable driving behavior in the highway scenario. Crucially, when statistically controlling for cognitive load, the effect of visual load emerged significantly in the dual-task context but was absent in the low cognitive load rural condition. The study found that participants with degraded vision exhibited increased speed variability and SDLP during the highway scenario, indicating poorer lane-keeping and speed control. These impairments were more pronounced in the group with higher visual degradation (6/75) compared to the group meeting the legal threshold (6/15). The findings suggest that static visual acuity measurements alone are insufficient predictors of driving safety, particularly in modern driving environments characterized by increased dashboard displays and multitasking demands. The study emphasizes the importance of meeting visual needs at all distances, including intermediate distances required for in-vehicle devices. It implies that drivers with vision at the legal threshold may still experience significant performance deficits when cognitive resources are taxed, highlighting the need for a more comprehensive assessment of visuo-cognitive capacities in driving fitness evaluations.
Key finding
Reduced visual acuity significantly impairs driving behavior only when combined with high cognitive load, whereas its effect is not present in low cognitive load conditions.
Methodology
simulator
Sample size: 21
Provenance
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | Crossref | — | — | 1 | 2026-06-05 |
| archive | success | canonical_url | — | — | 1 | 2026-06-06 |
| extract | success | cached | — | — | 3 | 2026-06-10 |
| clean | success | clean | — | — | 1 | 2026-06-07 |
| chunk | success | chunk | — | — | 1 | 2026-06-07 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-07 |
| promote | success | — | — | — | 1 | 2026-06-05 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 2 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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- Empirical Findings: behavioral performance data
- Methodological Resource: tool software
- Theoretical Contribution: theory or model