Effects of In-Vehicle Messaging on Mental Workload During Driving through Work Zones

Craig, Curtis M; Achtemeier, Jacob; Patzer, Brady; Morris, Nichole L · 2017 · Crossref

DOI: 10.17077/drivingassessment.1632

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Summary

This study investigates whether in-vehicle smartphone messaging can effectively warn drivers of hazards in work zones without increasing mental workload, addressing the limitations of traditional roadside signage which often fails to reduce speeds or capture driver attention. The research was motivated by the high risk of crashes in volatile work zone environments and the potential for task-relevant smartphone messages to be less disruptive than task-irrelevant distractions. The authors specifically examined how message modality (audio-only vs. audio-visual) and device placement (dashboard vs. passenger seat) influenced mental workload, usability, and event recall. The experiment utilized a driving simulator with 48 participants who drove through two distinct rural work zone routes: one featuring a shoulder closure and another with a lane closure. The study employed a mixed factorial design comparing three message modalities: a control condition using portable changeable message signage (PCMS) on the roadside, an in-vehicle audio-only message, and an in-vehicle audio-visual message. Smartphone placement was a between-subjects factor, with devices mounted either on the dashboard or the passenger seat. Participants performed a secondary cognitive load task (backwards counting) concurrent with driving. Data were collected using the Rating Scale Mental Effort (RSME) for workload, the System Usability Scale (SUS) for usability, and free-recall tests for message retention. Results indicated that both in-vehicle messaging conditions significantly reduced mental workload compared to the roadside signage control. RSME scores were highest for the control condition and significantly lower for both audio-only and audio-visual conditions, with no significant difference between the two in-vehicle modalities. Similarly, usability scores were significantly higher for the in-vehicle systems than for roadside signs. Regarding recall, the audio-only condition yielded significantly better event retention than the control condition. A significant interaction revealed that for the more complex lane-closure route, recall was superior for in-vehicle messages when the phone was placed in the passenger seat, suggesting that visual attention was more focused on the road rather than scanning for distant signage. The study concludes that in-vehicle smartphone messaging is a promising strategy for improving driver safety in work zones by reducing mental workload and enhancing information retention compared to traditional signage. Although audio-visual and audio-only systems performed similarly on objective measures, participants strongly preferred the audio-only modality, likely due to concerns about visual distraction. The findings suggest that in-vehicle systems allow drivers to allocate visual attention more efficiently to the driving task, and that device placement in the passenger seat does not hinder effectiveness, particularly in high-demand driving scenarios.

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Topics

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• mental demand
• auditory
• external distraction
• road complexity
• visual
• cognitive

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• Applied Guidance: design guidelines
• Empirical Findings: physiological data
• Theoretical Contribution: theory or model