A literature survey was performed on the glare and distraction of a new type of headlamps with a bluish colour, such as gas discharge lamps or lamps with coloured bulbs or reflectors. It is concluded that lamps with a cool, bluish colour produce more discomfort glare and are perceived brighter than lamps with warm more yellowish light. There is no evidence that disability glare is colour dependent. Averaged over studies on automotive, public and interior lighting, it can be concluded that every 100 K increase in colour (correlated) temperature the luminous intensity must be lowered almost 4% in order to maintain a constant discomfort glare level. In field experiments, it was found that in order to produce the same discomfort glare levels, tungsten-halogen headlamps can be set a factor 1.46 to 2 higher photopic light levels than gas discharge lamps. A model based on laboratory data of monochromatic and bichromatic light sources, which assumes that the scotopic efficiency function is the action spectrum for discomfort glare, predicts only a factor 1.09. Possible candidates for the explanation of this difference between field and laboratory results are the light spectrum, the experimental ambience, and the unfamiliarity with the relative new gas discharge lamps. No studies on distraction of bluish car headlamps were found. However, it is expected that the bluish will distract road users, especially when the intensity or colour of the light is fluctuating. It is not clear what the combined effect on discomfort glare is of the relevant headlamp parameters, luminous intensity, size, colour, and temporal stability. This should be considered when the requirements for headlamps are modified. In order to establish requirements for the luminous intensity and colour of headlamps, the knowledge on the current discrepancy between laboratory and field studies and the effect of the dynamic character of headlamps on traffic safety should be extended. (A)
Abstract