So you thought you only had two brake lights.  Look again and you'll see one in the center at a higher level than the two on either side of the vehicle.  They're sometimes in the inside of the vehicle behind the back window, or they could be in the deck lid, on the roof or on the spare wheel carrier,

But why is that third brake on your vehicle? Experts say it helps prevent rear end collisions. Tests done by installing the third brake light in taxis and fleet vehicles showed fewer rear end crashes in the ones that had the extra light. The third brake light was mandated in new passenger cars in 1986 in the US and Canada.  The requirement was added to new light trucks and vans in 1994.

Sometimes it's difficult to know if your third brake light is even working.  Many vehicles have bulb warning systems that alert you to non-functional bulbs, but not all do. Your vehicle service facility will often check to see if all your turn signals, taillights and headlights are working during routine maintenance inspections, and they may notice that the third brake light is out. 

So, do you have to have it replaced? Not necessarily. Many areas only require one brake light to work in the rear of a vehicle. So even though new vehicles have to have the third brake light, you may not get a ticket if it eventually stops working.  But you may be missing an opportunity to drive a safer vehicle if you don't get it fixed.

In 1995, an insurance institute study found that 1986 model cars were involved in 5 percent fewer rear-end collisions from 1986-1991 than they would have expected without the extra light.

Ask your service advisor for advice.  Keep in mind that in these days of drivers distracted by everything from texting to putting on makeup while driving, you can reasonably conclude that anything that makes you more visible to the vehicle behind you adds one more—possibly life saving—safety margin. 

Auto Lab Troy
2790 West Maple Rd.
Troy, Michigan 48084
(248) 643-7690