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

Area of Science:

• Road safety
• Automotive engineering
• Traffic accident analysis

Background:

• The center high mounted stop lamp (CHMSL) was introduced as a mandatory safety feature in U.S. vehicles starting with the 1986 model year.
• Its primary purpose is to enhance the visibility of braking signals to drivers of following vehicles, thereby aiming to reduce rear-end collisions.

Purpose of the Study:

• To evaluate the effectiveness of the center high mounted stop lamp (CHMSL) in reducing the incidence of rear-end vehicle collisions.
• To compare the rear-end collision rates between vehicles manufactured before and after the CHMSL mandate.

Main Methods:

• Utilized insurance claims data for vehicle damage to assess collision rates.
• Compared rear-end collision frequencies for model year 1985 (pre-CHMSL) and model year 1986 (post-CHMSL) vehicles.
• Adjusted collision data for differences in vehicle age to ensure a fair comparison over the calendar years 1986-1991.

Main Results:

• Model year 1986 vehicles equipped with CHMSL experienced 5% fewer rear-end collisions compared to the expected rate.
• The reduction in collisions was observed after accounting for variations in vehicle age and exposure time.

Conclusions:

• The mandatory implementation of the center high mounted stop lamp (CHMSL) has demonstrated a measurable positive impact on road safety.
• CHMSL effectively improves braking signal recognition, leading to a significant decrease in rear-end collisions and associated vehicle damage.