Effective Indicators of Partially Automated Truck Platooning [techbrief]

Roldan, Stephanie M.; Gonzalez, Tracy B. · 2021 · ROSA P / United States. Federal Highway Administration. Office of Research, Development, and Technology

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Summary

This research addresses the safety and public acceptance challenges associated with the impending commercial deployment of partially automated truck platooning in the United States. As platoons of two to four trucks equipped with cooperative adaptive cruise control (CACC) begin operating on public roads, their close-distance following behavior may pose physical obstacles and safety concerns for other road users. Conversely, disruptive behaviors by non-platoon vehicles, such as cutting in between trucks, threaten the operational efficiency and fuel savings of platooning. The study was motivated by the lack of established standards for communicating platoon status to surrounding drivers and the need to understand how light-vehicle drivers perceive and interact with these heavy-vehicle formations. The researchers conducted two experiments to identify effective communication strategies. Experiment 1 surveyed 50 participants to determine how drivers label, perceive, and plan behaviors around single and grouped trucks, exploring attitudes toward both conventional and automated platoons. Experiment 2 involved 48 new participants who viewed static simulated scenarios of a two-truck platoon. Participants first assessed control scenarios without signs, then evaluated scenarios featuring four sets of novel signs or indicators developed based on Experiment 1 findings. These included roadside-mounted signs, truck-mounted signs, and light bars, with specific wording variations such as "convoy" and "linked convoy." The study measured participant judgments regarding navigation, safety, and expectations for platoon operations. Results from Experiment 1 revealed that 54% of respondents felt anxiety or fear near heavy trucks, and 91% altered their driving behavior around them. Drivers often interpreted short following gaps as aggressive rather than cooperative. The term "platoon" was unfamiliar to most participants, with 72% preferring "convoy" to describe automated truck groups. Experiment 2 demonstrated that signs significantly improved comprehension and safety perceptions. In unsigned scenarios, less than 20% of participants expected trucks to maneuver in tandem; this increased to over 60% when signs were present. While the term "convoy" was preferred in Experiment 1, signs using this term were perceived as less cooperative in Experiment 2, likely due to associations with conventional driving. The most effective intervention was a combination of roadside and truck-mounted signs (R2 and T2) identifying the group as a "linked convoy," which yielded the highest ratings for comprehension, perceived safety, and legibility. The study concludes that explicit signage is an effective method for supporting driver comprehension, safety, and acceptance of heavy-truck automation. Short following gaps alone are insufficient to signal cooperative behavior to other drivers. The findings suggest that standardized indicators, particularly those combining roadside and truck-mounted messaging, can mitigate safety risks and improve public trust. Future research will evaluate these specific signs in dynamic driving simulator scenarios to further assess their impact on driver behavior during freeway entry and exit.

Key finding

Novel roadside and truck-mounted signs identifying a platoon as a 'linked convoy' significantly improved road users' comprehension of platoon operations and increased perceived safety ratings compared to unsigned scenarios.

Methodology

mixed_methods

Sample size: 98

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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