Since 1986, all new vehicles in Canada and the United States have been by law equipped with a centre high mount stop lamp (CHMSL). This brake light is higher than the left and right brake lights, centrally, near the back of the vehicle. The location parameters are precisely defined, and leave no doubt for the manufacturers.
The law was initiated by the United States Department of Transportation under President Reagan. His administration was generally in favour of limiting the role of government and government regulation. Nevertheless, under this administration the automobile, after a long history of having two brake lights, suddenly had to be with an additional brake light of uncertain value. It seems to have been, to some degree, one of those “well, it can’t hurt” decisions.
Statistics were cited at the time of the 1986 legislation regarding the experience of fleet operators using the CHMSL. There was a claim of 50% reduction in rear-end collisions, presumably in relation to pre-CHMSL fleet accident rates.
The cost of installation of the CHMSL in the context of mass production is relatively inexpensive. The light is located more or less at “eye level”. Generally, it is inside the rear window. However, on more exotic vehicles, it is sometimes on a custom-designed mounting pod or attached to the rear spare tire cover.
Manufacturers have some discretion on the nature of the lighting technology. They use central filament bulbs, along with LEDs and more recently, neon tubes. Making a virtue out of a necessity, some manufactures have by now introduced elegantly designed CHMSLs that are an adornment rather than an eyesore, and this progression is rapidly becoming the norm.
Pay attention to the light
The idea is that the CHMSL will attract the attention of following drivers when other vehicles block the view of the right and left brake lights. Assuming all vehicles are the same height, the drivers of a line of traffic will see the CHMSL light when active, following the vehicle displaying the active CHMSL.
Recent studies suggest that the universal use of CHMSL results in about a 5% reduction in collisions. 5% is a big number in the overall context of traffic accidents. If the number is even close to being correct, the CHMSL is a noteworthy success.
One troubling development in relation to the CHMSL is the use of the frame of the lamp as a mounting bracket or support for the “N” sticker required under the graduated licensing program. It is not unusual to see an “N” sticker inserted between the CHMSL and the rear window of a vehicle, obscuring partially or entirely, the lamp. The driver, in disabling the proper functioning of an important stop lamp, demonstrates a serious lack of what we might call “safety consciousness”.
We do not necessarily need more laws and regulations at the moment to deal with the disabling of the CHMSL, just an enforcement of common sense in this regard.