Effects of motorway lighting on workload and driving behaviour

The Dutch Ministry of Transport, Public Works and Water Management needs knowledge in the area of workload in car driving. This paper describes a study in which the effects of traffic volume, road lighting, and a cognitively loading secondary task on driving behaviour and workload were investigated. In a field experiment, subjects drove a fixed route in a TNO instrumented vehicle on a motorway, on which the public lighting was experimentally manipulated. Measurements were started at the beginning of the evening, yielding runs in busy as well as in quiet traffic conditions. In half of the runs, 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 (ECG and EOG). After each run, subjects completed a questionnaire that measured the subjective rating of mental effort. We expected the workload to be higher in dense traffic, on an unlit road, and while executing the secondary task. Results showed that traffic flow intensity and the presence of the secondary task both affected speed choice and workload (both physiological and subjective measures). When conducting the secondary task, subjects carried out fewer overtaking manoeuvres. Motorway lighting especially affected the steering reversal rate, the eye blink frequency, and the steering effort