Effectiveness estimates for center high mounted stop lamps: A six-year study

The center high mounted stop lamp is a supplemental brake light mounted at the height of the rear window that has been required on all new cars sold in the US starting with the 1986 model year. It was intended to reduce the number of rear-end collisions by improving the braking signal recognition of following drivers. Insurance claims for vehicle damage were used to compare the rear-end collision rates of model year 1985 and model year 1986 cars over calendar years 1986–91. After adjusting for the difference in vehicle ages, model year 1986 cars were found to have experienced 5% fewer rear-end collisions than would have been expected without the center high mounted stop lamps.