Behavioral Aspects of Automatic Vehicle Guidance: Relationship Between Headway and Driver Comfort

Abstract

Automation of road traffic has the potential to greatly improve the performance of traffic systems. The acceptance of automated driving may play an important role in the feasibility of automated vehicle guidance (AVG), comparable to automated highway systems (AHS). Because decreasing headways could mean a large increase in road capacity, a study was conducted concerning the acceptability of short headways in an automated traffic system. In one part of a driving simulation experiment, subjects gave ratings on comfort regarding the headway in an automated lane; in another part of the experiment, subjects were allowed to adjust the headway setpoint to a comfortable level. Subjects also rated the comfort level when driving under manual control in a number of traffic conditions. Results showed that to equal the comfort level that people experience daily in dense traffic on the freeway network in rush hours, the AVG headway should be no less than 0.86 sec. If a comfort level that people experience daily during incident situations (not uncommon in unstable traffic flow) would be acceptable, the AVG headway could be as short as 0.29 sec. The AVG headways as set by the subjects correspond to the values observed in normal traffic (on average 1.1 sec).