Understanding Roof Crush

Consumers have no way of knowing when they buy a car or truck whether the roof will protect them in a rollover crash. The strength of a vehicle’s roof is measured by what manufacturers call the ’’strength to weight ratio’’. the federal standard governing minimum roof strength was passed in 1971. The standard only requires that the manufacturer meet a strength to weight ratio of 1.5 times the weight of the vehicle. Some manufacturers design their roofs to have exceptionally good strength while others do not. Some manufacturers design down to the minimum standard of 1.5 times the vehicle weight. It is obvious that in a rollover the strength of the roof must significantly exceed one and a half times the weight of the vehicle. Rollover forces are much higher than that.

To pass the current federal standard, a car must withstand basically being placed on its roof and one half of its weight being gently put on a bottom of it. If the vehicle can support the weight plus one half with less than five inches of roof crush, it will pass the standard. Obviously, that is inadequate roof support. Fortunately, NHTSA recently saw the error of its ways and in December of 2009 passed a rule that will double the strength of vehicle roofs of passenger cars and light trucks starting in 2012. In the meantime, the Insurance Institute for Highway Safety will be adding a new roof rating system. It is important that the public understand what they’re buying. In order to receive a marginal rating from the Insurance Institute, minimum strength to weight ratio of 2.5 will be requires. An acceptable rating will be 3.25.

To receive a good rating the vehicle must withstand a force of four times the vehicles weight before reaching five inches of crush. Anything lower than a 2.5 will be considered a poor vehicle. There are many vehicles on the road that have less than 2.5 strength to weight ratio. There are serious injuries , including quadriplegia and deaths resulting from these extremely poor roofs. The cost of the vehicle is not related to roof strength .there are some very inexpensive vehicles that have very strong roofs. NASCAR drivers and their car builders have known for years of the need to have a strong roof. These cars can roll over many times and the occupant usually escapes injury.

Someday manufacturers will design the roofs to protect the occupants. And someday the federal government to mandate stronger roofs.

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