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An Evaluation of a Collision Avoidance Brake Light System

Sponsoring partner: Department for the Environment, Transport and the Regions


A significant proportion of traffic accidents are classified as front-to-rear-end crashes (shunts). Research indicates that drivers may not always accurately perceive the actual deceleration of a lead vehicle to determine an appropriate braking response. Brake lights are an important signal of vehicle braking. However, despite developments to improve conspicuity of the brake light (e.g., lens design, light source, high mounting), its information value remains limited. Brake lights only indicate the activation of the brake system. They do not convey hazard information about the response of the vehicle in terms of a change in velocity. This is a significant limitation as it is the deceleration of the vehicle rather than the activation of its braking system that is important for traffic safety. The aim of this research was to evaluate an innovative rear brake light system to inform traffic of the degree of hazard, i.e. the extent of deceleration of a vehicle during a braking manoeuvre. The proposed Collision Avoidance Brake Light System (CABLS) was comprised of an oversized high intensity LED array attached to the standard Centre High-Mounted Stop Lamp (CHMSL). The extent of illuminated array corresponds to the extent of the deceleration by the vehicle - the greater the deceleration, the more array lights are displayed). The LADS was used to study and evaluate the concept of a CABLS. Specific hazard scenarios were generated in the simulator to assess subject perceptions of the braking system and response to traffic braking. The evaluation compared informative and random CABLS formats to the standard CHMSL configuration to evaluate the information and conspicuity value of the proposed system. Results showed that whereas the CABLS did not improve safety under the evaluation conditions of this study, there was evidence that it does result in differentiated responding to traffic events depending on the magnitude of deceleration defining a braking event when following in traffic. Not all subjects could infer the function of the display accurately, however, the concept when explained to drivers was endorsed as having potential to improve traffic safety.