Werkbelasting en rijgedrag tijdens duisternis : eerste veldexperiment. In opdracht van het Directoraat-Generaal Rijkswaterstaat, Adviesdienst Verkeer en Vervoer AVV.

Rijkswaterstaat from the Dutch Ministry of Transport, Public Works and Water Management needs knowledge in the area of workload in car driving. This report is the result of a first project phase, in which we investigated which set of methods has the highest potential for measuring workload effects in various driving situations, using public road lighting as a case. Using literature and available knowledge, we made a selection of candidate measures. Next, we conducted an experiment to investigate to what extend these measures are suitable to establish differences in workload. In this experiment, subjects drove a fixed route on a motorway, on which the public lighting was experimentally manipulated. The subjects also had to perform a cognitively loading secondary task. During the runs we registered the driving behaviour as well as a number of physiological variables (heartbeats, breathing and eye blinks). After each run, subjects completed a questionnaire that measured the subjective rating of mental effort. We expected the workload to be higher on an unlit road, and while executing the secondary task. We found effects of lighting and of the secondary task on speed choice and in the physiological measures (heartbeat, breathing and eye blink frequency) and in the subjective ratings. Lighting also influenced the steering effort. When conducting the secondary task, subjects carried out fewer overtaking manoeuvres. Removing roadway lighting or adding a secondary task yields an adaptation of driving behaviour: drivers reduce their speed, and overtake less often when conducting a secondary task. In spite of these behavioural adaptations, workload without lighting or with a secondary task was higher. These were additive effects. Hence, the effects of the lighting are not altered by the secondary task. The value of the secondary task performance as a dependent variable (i.e., to measure ‘spare capacity’) has not been demonstrated. In this study, we found effects of roadway lighting on driving behaviour and workload, whereas some earlier studies did not yield such effects. This shows that the research method we used was an adequate choice. (Author/publisher)