Using an automated speed, steering, and gap control system and a collision warning system when driving in clear visibility and in fog

Bloomfield, John R.; Grant, Angela R.; Levitan, Lee; Cumming, Tammie L.; Maddhi, Srinivas; Brown, Timothy L.; Christensen, J. Marty · 1998 · ROSA P / United States. Federal Highway Administration

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Summary

This study investigates the impact of automated highway systems on driver performance, specifically examining an automated Speed, Steering, and Gap Control System (SSGCS) and a Collision Warning System (CWS). Conducted in the Iowa Driving Simulator, the research aimed to determine how these intelligent vehicle systems affect driving behavior under varying conditions of visibility (clear vs. fog) and traffic density. The study involved 52 drivers, divided into an experimental group of 32 participants with access to the systems and a control group of 20 participants without access. The experimental design accounted for driver age and traffic density to assess their interaction with the automated technologies. The results revealed distinct behavioral changes depending on which system was active. When drivers used the SSGCS, there was no significant effect on average velocity; however, drivers tended to maintain a larger following distance behind the vehicle ahead compared to the control group. Conversely, when only the CWS was engaged, drivers demonstrated more precise control over both speed and steering, likely due to increased attention to the driving task. Notably, CWS users traveled at higher speeds than controls, particularly in 100-meter fog conditions, potentially indicating testing behavior. The CWS alone did not affect following-distance measures. When both systems were disengaged after prior use, experimental group drivers exhibited mixed performance changes compared to controls. While minimum following distances remained unchanged, experimental drivers displayed more frequent steering oscillations and velocity fluctuations. Despite these increased correction frequencies, their overall steering instability did not change, and they actually reduced velocity instability by making smaller, more frequent speed adjustments. These behaviors suggest that the cognitive load of deciding when to engage or disengage the systems heightened driver attention. Lane-changing behavior and gap acceptance were also analyzed, though the primary findings focused on longitudinal and lateral control metrics. The study concludes that while automated systems like the SSGCS and CWS do not drastically alter average speed or minimum following distances, they significantly influence the precision and frequency of driver corrections. The findings imply that the presence of such systems alters driver engagement, leading to more meticulous control inputs even when the automation is inactive. This research provides critical insights for the development of Intelligent Transportation Systems, highlighting the need to understand how automation affects human factors, attention levels, and driving stability in complex environmental conditions like fog.

Key finding

Drivers using the SSGCS maintained average velocity but increased following distances, while those using only the CWS controlled speed and steering more precisely than controls, particularly in fog.

Methodology

simulator

Sample size: 52

Provenance

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

Topics

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• speed distance perception
• following distance
• traffic density
• speed choice
• visual occlusion
• automation surprise

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: behavioral performance data
• Methodological Resource: tool software
• Theoretical Contribution: computational model