So far, the luminous intensity has been prescribed by law as a photometric quantity to describe the brightness of signal lights. It describes the perceived brightness impression in the far field, where visual objects appear as points. The aim of this work is to determine the relevant luminance for the brightness impression in the near field for tail and brake lights. Various influencing parameters were taken into account, such as aging and soiling of the signal light, the age of drivers, and different weather conditions. To compensate for these influences, the luminance of the illuminated area of signal lights must automatically and dynamically adjust. Based on the results obtained, an adaptive signal light system was ultimately defined.