EFFECT OF THE CENTER HIGH-MOUNTED STOP LAMP ON VANS AND TRUCKS

The study assessed the effect of the Center High-Mounted Stop Lamp (CHMSL) on vans and trucks. The CHMSL effect was assessed by measuring the Brake Response Time (BRT) of unsuspecting drivers in the traffic stream. A total of 1,087 trials were run with four types of vehicles and the CHMSLs mounted in two positions. The results showed a small but statistically significant reduction in BRT of .09 seconds when the CHMSL was in use. The effect of the CHMSL did not vary significantly as a function of vehicle type, CHMSL position, headway, speed, or time of day. The magnitude of CHMSL effect is smaller than that observed in braking trials on automobiles prior to their required installation beginning with the 1986 model year. Whether the difference in BRT reduction is due to the size and shape of vans and trucks, a decrease in CHMSL effect or earlier overestimation of the original CHMSL effect cannot be ascertained from available data.