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You & Your Car

The lowdown on bumper height Add to ...

Although I’ve noticed pickup trucks raised to ridiculous heights in the past, I was amazed recently when I stopped to allow one to back out of an angled parking spot; he backed up a little far and partially over the hood of my old Alfa Spider (no damage). I don’t want to have one of these behemoths run over me. I thought there were strict bumper height regulations. Am I right or wrong? – Bob in Rossland, B.C.

Here is a case of good intentions, poor results and another where the distinction between passenger vehicles and light trucks is out of whack.

You are right, there are regulations regarding bumper height but they date back to 1971 and, despite having been modified several times since, do not address the preponderance of “light trucks” on the road. Remember, “light” trucks, in regulatory speak, includes minivans, SUVs and pickups. These three constitute the vast majority of passenger vehicles on our roads.

Bumper height regulations cover the crash damage permitted in low-speed collisions. Not only do they not take into account the difference in bumper heights between stationary vehicles – such as was the case in your experience, they do no allow for the dramatic change in bumper height created when braking.

When a vehicle brakes heavily, weight is transferred forward. The front suspension compresses, the front end dips and the rear end lifts accordingly. As a vehicle brakes heavily, the front bumper drops precipitously, allowing it to go under the rear bumper of the vehicle in front – if it is stationary. If the vehicle in front is also braking heavily, that same weight transfer that makes it nosedive lifts the rear bumper further into the air – allowing that following vehicle push even further beneath.

If the vehicles in front is a minivan, SUV or pickup its rear bumper will be far higher and the following vehicle go deeper under. That’s why you see, in some multiple-vehicle rear-end collisions, one vehicle atop another.

Regulatory bodies have been promising more effective bumper height regulations for many years, ones that take into effect more than stationary bumper height vehicle, but also compatibility including height, braking and suspension dynamics. Back in 2008, the U.S. Insurance Institute for Highway Safety asked the U.S. National Highway Traffic Safety Administration (the folks who set the regulations) to regulate bumper height on SUVs, pickups and minivans the same as cars. A year later, the NHTSA agreed to look into it but nothing has transpired yet.

 

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