The Effectiveness of Unimodal and Multimodal Warnings on Drivers’ Response Time: A Meta-Analysis

Driving warning systems are of great help in notifying emergencies. Based on the results of former studies as well as the multisensory integration effect (MIE), the current meta-analysis investigated the effectiveness of utilizing unimodal (i.e., auditory, visual, and tactile) and multimodal (i.e., bimodal and trimodal) driving warning systems in drivers’ response time. Sixty eligible articles representing 308 individual studies were included in this meta-analysis. The results showed: First, both auditory warnings (pooled Hedges’ g = 0.98, 95% CI: 0.34 to 1.61, p < 0.01) and tactile warnings (pooled Hedges’ g = 0.77, 95% CI: 0.22 to 1.32, p < 0.01) were found to reduce the response time significantly compared to no warning, but visual warnings did not produce significant benefit; Second, tactile warnings outperformed the visual warnings (pooled Hedges’ g = 0.74, 95% CI: 0.11 to 1.37, p < 0.05); Third, auditory-tactile bimodal warnings surpassed unimodal warnings (p < 0.05); Fourth, drivers’ response time under trimodal warning conditions were shorter than that under bimodal warning conditions but not in a significant level. Overall, the results support multisensory redundant signal effect hypothesis in multimodal conditions. Current study provides a quantitative understanding of the effectiveness of driving warnings and could contribute to the design of related technologies.