Since the invention of automobiles, rear lamps suffered from poor visibility in bad weather or due to lamp soiling. With the advent of advanced sensor systems and powerful microcontrollers, it is possible to adjust the light output of signalling applications to the visibility conditions. Latest LED technology allows to control the light output of signal lamps between almost zero cd and several hundred cd. Schefenacker has developed a system to improve the visibility of signal lamps by adaptation of the lighting levels to the environmental conditions. A detector system, consisting of a Lidar sensor and a combined brightness/dirt sensor detects the environmental conditions. A microcontroller transfers these data into necessary brightness levels for the intelligent rear lamp. The intensity of the signalling function is adapted accordingly, to guarantee a consistent perception even under bad weather conditions. This will affect positively the road safety, especially under strongly varying brightness conditions and in foggy weather. The system offers also the opportunity to get an automatically working fog lamp. Finally, the legal situation is highlighted. Since the implementation requires continuously varying intensity levels, the respective ECE regulations have to be adopted. Extensive work has been done since the first ideas for an adaptive tail lamp, and it is expected that the regulations will be adapted soon.