A characteristic for the asymmetrical low beam headlight is the definition of a light-dark boundary, figure above. For the right-hand traffic it runs horizontal to the left away from the vehicle axis and to the right it rises at an angle of 15°. In the longitudinal direction of the vehicle, the light-dark boundary with reference to the headlight centre, moves downward, lowered by 1 %, i.e. around 25 cm over a distance of 25 m.
Above the light-dark boundary is the area of glare. The intensity of light from the low beam should not amount to more than 1 lx, 25 m in front of the vehicle. Within the area of oncoming traffic, this limit value amounts to only 0.6 lx. Below the light-dark boundary, a high intensity of light is desired.
Apart from the lighting power, the number and the location of headlights is also prescribed by law. For example, the headlight low beam in multi-track vehicles requires at least two lights. For the high beam at least two, but at the most four headlights are allowed.