Evaluating the effects of bilingual traffic signs on driver performance and safety

Jamson, Samantha; Tate, Fergus; Jamson, A. Hamish · 2005 · OpenAlex-citations

DOI: 10.1080/00140130500142191

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Summary

This study investigates the impact of bilingual Variable Message Signs (VMS) on driver performance and safety, motivated by the need to accommodate speakers of minority languages in bilingual countries like Wales. The primary research question addresses whether the visual distraction caused by bilingual signs, which present double the text volume with half being superfluous to monolingual drivers, degrades driving behavior. The authors hypothesized that increased sign complexity and language count would impair performance, necessitating an evaluation of sign configurations to optimize safety. The researchers employed a driving simulator to ensure controlled, repeatable testing of various sign configurations. Twenty-four participants, equally divided between monolingual (English) and bilingual (English/Welsh) drivers, navigated a simulated rural motorway. The experimental design manipulated sign complexity (one to four lines of text) and language presence (monolingual vs. bilingual). Driver performance was assessed under two workload conditions: a low-workload scenario with a constant-speed lead vehicle and a high-workload scenario with a variable-speed lead vehicle. Data collection focused on longitudinal measures (speed, headway) and lateral position, alongside subjective mental workload ratings using the NASA TLX. The results indicated that drivers could read one-line and two-line monolingual and bilingual signs without significant disruption to their driving behavior. However, exposure to four-line signs, whether monolingual or bilingual, caused significant performance degradation. Drivers significantly reduced their speed by approximately 3–11 km/h and increased their headway to the lead vehicle to allocate more time for reading. This suggests that drivers were processing the irrelevant text on bilingual signs rather than ignoring it. Notably, there were no significant differences in performance between monolingual and bilingual participants, implying that bilingual drivers also struggled to filter out the non-preferred language. Subjective workload scores confirmed that the high-workload condition increased mental demand and effort. The study concludes that bilingual VMS configurations with four lines of text pose a safety risk by inducing visual distraction and altering driving dynamics. The findings imply that drivers do not efficiently ignore superfluous text, leading to increased reading times and reduced attention to the road. The authors suggest that design interventions, such as optimizing language sequence or using visual demarcation like separation lines, may be necessary to mitigate these effects. This research provides empirical evidence for traffic sign designers and policymakers, highlighting the need to limit text length and complexity in bilingual signage to maintain driver safety and performance.

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Topics

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• external distraction
• signage environment