The limitations of human information processing capabilities areapparent in modern road traffic. Research methods for studying roaduser behavior range from unobtrusive observations of actual trafficto highly controlled laboratory experiments. Often the incompatibility between controllability and validity makes the choice of a suitable method difficult. Described in this paper are recent developments in two research methods used at the tno institute for perception. In-car measurements using an instrumented car enable a detailed analysis of the behavior of the individual driver. The behavior of arbitrary road users can be analyzed quantitatively by outside measurements with video techniques. Recently developed computer-based techniques allow the quick, efficient, and flexible use of both methods. Themethods are illustrated by examples of recent research in which driver behavior is analyzed in terms of time-related measures. At the control level of the driving task, several results can be explained by the time-to-line-crossing (tlc) measure. At the guidance level, the time-to-collision (ttc) measure defines the severity of interactions between road users. The correspondence between the results of both approaches suggests that drivers directly use such time measures for vehicle control and decision making strategies in traffic. This paper appears in transportation research record no. 1213, Human performance and highway visibility: design, safety, and methods.
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