This study investigated the effects of lamp specification, lighting color, and ambient illumination on Center High Mounted Stop Lamps (CHMSL) brake reaction time (BRT) There are three specifications of lamp (5 W, 10 W, and 18 W, three levels of lighting color (yellow, red, and blue), and two levels of ambient illumination (daytime and nighttime) Results indicated that the CHMSL specification, light color, ambient illumination, and interaction of light color and ambient illumination were the significant factors to the BRT and perception time (PT). The BRT and PT with 5 W were less than with 10 W and 18 W. BRT and PT of light with yellow and red color were less than with blue. The BRT and PT in nighttime were also less than in daytime. Because of the effects of the 3 independent variables to movement time (MT) were not significant and result of correlation analysis, we conclude that the faster or slower of the BRT may be due to the PT.