Running light-twilight conspicuity and distance judgement


Type de document
Résumé / Abstract
The first problem of the present paper was to find out in which way vehicle conspicuity in various levels of twilight is influenced by the use of running lights. Three running light intensities, 100, 200 and 300 cd were used. The results indicate that no increase in conspicuity occurs until the sky illumination is down at about 1000 lux. Very small differences were found between the different light intensities. The second problem studied dealt with the effect of running lights on distance judgement to oncoming vehicles. Two psychophysical methods were used: a method of adjustment and a method of constant stimuli with limited exposure time. The running light intensities in the first part were 100 and 300 cd. No effect of light intensity was found. The running light intensities using the second method were 300 and 900 cd. The results here indicate a tendency to underestimate the distance to a vehicle with running lights. The underestimation increases with increasing running light intensity. The results from these two experiments suggest that the main conspicuity increment as a result of the use of running lights occurs at daylight levels below 1000 lux sky illumination. The use of running lights also seems to increase the safety margin to oncoming vehicles since the subjective distance is shorter than the objective one.

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