Car headlamps: Influence of dirt, age and poor aim on glare and illumination intensities

Abstract

Luminous intensities of the low beam of private car headlamps in the direction of the eyes of drivers of oncoming cars (glare intensity), and of the right roadside (illumination intensity) were measured on the road (354 cars) and in the laboratory (50 cars). In the laboratory measurements the effects of aiming, cleaning and voltage adjustment of the headlamps were studied. Results are compared with the requirements of regulations for new headlamp types. Glare intensities were found to be much higher than the maxima permitted by the regulations. The main causes are dirt and lamp age. Excessive illumination intensities are mainly due to poor aim. The use of halogen lamps does not contribute appreciably to the high glare intensities found in practice. 20% caf new lamps were found to contravene regulations.