When driving gets bumpy

In the universe of auto accidents, there are high-speed crashes and rollovers at one end of the scale. And at the other end, you have the slow-motion bump.

Bumps of anywhere from 0.5 to 3 mph happen with remarkable frequency. Often, there is no visible damage to either car, and then the question becomes: Was it even an accident? Is it worth checking for hidden damage? Should you demand repairs for paint smudges? And how much slack should you cut a total stranger?

A lot of trends have made bumps more of a problem in recent years and are making it more difficult to simply excuse them as part of the normal urban driving experience.

Lease companies often demand that cars be returned in perfect condition, a ridiculous but widespread practice. More and more people are opting for expensive vehicles they cannot really afford and believe they must aggressively protect their investment. And finally many auto manufacturers have developed designs that offer zero protection against major damage to bumpers from very low speed accidents.

Many drivers mistakenly assume that when they are driving slowly, they can divert their eyes from the road ahead. Some bumps, for example, occur when a car in front is making a turn and then stops, while the next driver assumes the way has cleared and is looking to the side to make the same turn and then bumps the stopped car in front.

So, bumps result from bumbling human mistakes rather than aggressive speeding or high-risk lane changes or drunk driving. It’s the sort of mistake that compels even complete strangers to say, let’s just forget it; it’s part of sharing the road with 12 million other people in a densely compacted highway system.

“I would just say I am driving in L.A. and this happens,” said Ken Zion, an auto body repair expert who runs Automotive Collision Consultants. “Grin and bear it. It could happen in a parking lot, and you wouldn’t even know it.”

The theory is that nobody is perfect and even though you may be the bumpee today, you may be the bumper tomorrow.

Auto insurers say drivers involved in any bump should exchange insurance information and file claims, even if there is no damage. They advise against offers by the bumper to pay for damage to the bumpee without filing an insurance claim.

“If you don’t report it to your insurer, you are not going to have coverage,” said Candysse Miller of the Insurance Information Network of California. It may look like there is no damage, but internally there could be damage.”

If no damage, injury or claim occurs, it may not make any sense to have an accident put on your driving record. Miller is correct, however, that the appearance of no damage can be deceiving.

It is extremely difficult for ordinary drivers to judge whether a bump is severe enough to cause damage to the energy absorbing system in the bumper, Zion says. At one time, federal safety standards aimed to eliminate costly damage from minor bumps.

Before 1982, federal safety standards required cars to have bumpers that could withstand a 5-mph collision and not cause any serious damage to the car’s frame or body and only inconsequential damage to the bumper itself. But the Reagan administration established new rules that lowered the standard to 2.5 mph and eliminated the part of the standard that applied to the bumper itself.

So even a 2-mph bump may not damage the frame or body of a new car, but it can cause a lot of damage to the bumper. Bumpers are looking less like bumpers all the time on new cars, instead sporting complex shapes that mould into the rest of the car. On the Volkswagen Beetle, for example, the bumpers flow almost seamlessly into the fenders.

Typically, auto makers use plastic bumper covers over a foam-and-steel core. A minor bump may allow the plastic to bounce back but cause the foam to remain deformed. The rule of thumb in the auto body industry is to replace the foam core if it has any deformation, even though it may not be important functionally.

As collision speeds increase, the bumper system’s pistons, crushable cans or deformable brackets may be “stroked” -- or compressed -- to absorb energy from the crash. If they are stroked, then the rule of thumb is that they must be replaced. And finally, a bump that activates the energy absorbing bumper system above 2.5 miles per hour may also deliver enough wallop to cause minor but important deformation of the body.

Even if there is only microscopic cosmetic damage, more and more people want it fixed, said Don Feeley, who owns three auto body shops in Riverside.

“A lot of people want to say, don’t bother with it,” Feeley said. “But they are in a lease vehicle and are paranoid about damage that will cost them when they turn in the vehicle. The lease companies are giving you less wiggle room every day. The car has to come back in like it left. They shouldn’t even call them leases. They should call it a borrow.”

And often when somebody offers to cover damage out of their own pocket to somebody they have bumped, they have an unrealistic assumption about how much the repairs will cost. Feeley said a lot of people think you can paint or repair a bumper for $50 or $100.

“You can’t buy an ice cream cone for $50 in this business,” Feeley said.

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Ralph Vartabedian can be reached at ralph.vartabedian@

latimes.com.