The unit has at least one brake light (11) for emitting visible and/or infrared light influenced by acceleration information (s) detected in analogue form by a sensor arrangement (16). The acceleration information is held in a temporary memory (4) and electronically processed. A deceleration in excess of a certain threshold derived from a preceding acceleration leads to illumination of the brake light. The acceleration information can be detected by the vehicle's anti-lock braking system and fed to the memory.
