COMMENTS ON THE LIGHT INTENSITY REQUIRED FROM HEADLAMPS

By studying the distribution of light intensity in the vicinity of the headlight axis and by assuming that the illumination of obstacles must be 2 lux, the author shows that the sum of axial light intensities of all headlamps must be in the order of 300000 cd to ensure good visibility up to 600 M on a straight road. From experiments carried out in France, to determine the moment when drivers coming from the opposite direction request the change from full beam to dipped beam, it is possible to assess that such a light intensity is acceptable. To solve the problem of the black hole during this change, tests were conducted with an electronically controlled device, which enables the voltage at the lamp terminals, that produce the full beam and the switching on of the dipped beam, to be progressively reduced before complete extinction of the full beam. /TRRL/