Why do drivers maintain short headways in fog? A driving-simulator study evaluating feeling of risk and lateral control during automated and manual car following

Abstract

Drivers in fog tend to maintain short headways, but the reasons behind this phenomenon are not well understood. This study evaluated the effect of headway on lateral control and feeling of risk in both foggy and clear conditions. Twenty-seven participants completed four sessions in a driving simulator: clear automated (CA), clear manual (CM), fog automated (FA) and fog manual (FM). In CM and FM, the drivers used the steering wheel, throttle and brake pedals. In CA and FA, a controller regulated the distance to the lead car, and the driver only had to steer. Drivers indicated how much risk they felt on a touchscreen. Consistent with our hypothesis, feeling of risk and steering activity were elevated when the lead car was not visible. These results might explain why drivers adopt short headways in fog.

Practitioner Summary: Fog poses a serious road safety hazard. Our driving-simulator study provides the first experimental evidence to explain the role of risk-feeling and lateral control in headway reduction. These results are valuable for devising effective driver assistance and support systems.

Keywords:

• transportation safety
• human–machine systems
• driving
• virtual environments

Acknowledgements

The research of Mehdi Saffarian and Riender Happee is supported by the Dutch Ministry of Economic affairs through the program High Tech Automotive Systems (HTAS), grant HTASD08002 to the project Connect & Drive and grant HTASI09004–E!5395 to the project Driver Observation in Car Simulators. Mehdi Saffarian's research is also supported by the Natural Science and Engineering Research Council of Canada (NSERC) graduate scholarship program. The research of Joost de Winter is supported by the Dutch Technology Foundation (Stichting voor de Technische Wetenschappen, STW), the Applied Science Division of the Netherlands Organisation for Scientific Research (Nederlandse Organisatie voor Wetenschappelijk Onderzoek, NWO) and the Technology Program of the Ministry of Economic Affairs.