DRIVING AT DUSK AND THE CONSPICUITY ROLE OF VEHICLE LIGHTS

This paper is concerned with the potential visual problems a driver faces during dusk, and the role of vehicle lighting in making vehicles more conspicuous during this period. Relevant aspects, including driver vision, vehicle conspicuity, detection of a vehicle's presence, vehicle distance estimation, and masking, are discussed. Overseas research is reviewed and it is concluded that there are a number of benefits in the early use of effective vehicle lighting during the dusk period. An overview is given of the results of an observational study undertaken in south-east Queensland (latitude approximately 27 degrees S) of the use of vehicle lighting during dusk in a sub-tropical environment. The main factors which appear to influence the use of vehicle lighting, including season, weather, road type and vehicle type, are discussed briefly. The results indicate considerable variation in the use of vehicle lighting during dusk. Many drivers, especially on clear sunny days defer using headlights until the ambient illumination is very low. In these circumstances, whilst the sky is still relatively bright the forward view for a driver is considerably darker. These drivers showed a poor recognition of their vehicle lights' conspicuity value. Parking lights are used extensively during dusk, but evaluation of these showed that only about half could be rated as having any useful conspicuity value. The legal requirement to use headlights after sunset was found to be very ineffective. It is concluded that the earlier use of effective vehicle lighting during dusk should be promoted.