At 5 MPH, How Effective is a Bumper at Preventing Damage?

Vehicle bumper design in minor collision impacts

Most of us would probably think a bumper would withstand a 5 mph impact without damage. At one time, 5 mph and zero-damage allowance was a benchmark in the auto industry. The zero damage was not really “no” damage, but a federal requirement of no more than a 3/8” dent and a ¾” displacement of the bumper using the 5 mph threshold of impact.

That was the case until the bumper performance standard changed for passenger cars in 1982, and the NHTSA (National Highway Transportation and Safety Administration) amended the damage impact requirements to the car body and safety related equipment at barrier impact speeds of 2-1/2 mph across the full width of the bumper and 1-1/2 mph on the corners of bumpers.

What Happened to Tough Bumpers?

When the NHTSA reduced the impact test requirements from 5 to 2-1/2 mph for models built after 1983, they reduced the threshold of damage tolerance in half. How this affects you as a consumer is that bumper design changed, increasing the possibility of damage at 5 mph, not reducing it.

The new requirement also added a bumper elevation from the road surface to be between 16” to 20”. The caveat is that the new requirement in damage threshold and bumper elevation are for passenger cars only, not SUVs, minivans or pick-up trucks. Consider a minor collision impact with more substantial weight and a bumper not aligned at the passenger car level.

Shiny Grids On Front Of New Trucks At Car Lot

Changing the standard was in effect to reduce regulations for the auto industry, and to maximize fuel economy by reducing auto weight and length.

The thought process behind the change was that it was more costly long-term to support 5 mph bumper designs (with more weight and added car length) and increased gas usage than an auto with a 2.5 mph bumper design (lighter in weight), even if a consumer incurred the cost of a repair because of the greater allowance for collision damage to the bumper and attachments.

Facts, and Why They Matter

The assumption, in either the 5 mph or the 2-1/2 mph version of the standard, that bumper weight minimizes collision damage was found to be minimal in difference after extensive testing. But what did prove to be effect was bumper design. Factors, such as bumper elevation alignment as well as bumper width across the full vehicle versus bumper and corner guards, have effects on collision damage.

Not All Bumpers are the Same

All bumpers are not the same. They actually vary quite a bit, both in how they are constructed and their performance. Some bumpers are built for style versus protection. Other bumpers are designed to not protrude beyond the body parts, which can result in more damage in minor collision.

Bumpers vary in their build. While most are covered in plastic, underneath the reinforcement may be steel, aluminum, plastic or fiberglass. To absorb minor energy crash, an added layer of foam or plastic honeycomb resides in the bumper (to crush/collapse) to reduce force. Add to this the actual space between these layers and the sheet metal of the body, all these constructs affect how well a bumper minimizes damage.

Type of Damage Impact

Another consideration in resulting bumper damage is the type of impact. Flat-barrier impact means the vehicle hits another vehicle or element with consistent surface across the width of the bumper. The results of front-into-angle-barrier and rear-into-pole, not flat-barrier hits, may increase structural damage much more in a seemingly minor collision (upwards of $1000 and more in repair of some models). These types of hit can affect embedded components, such cameras and sensors in newer model bumpers.


Bottom line, bumper design matters in how damage is minimized.

> Inspect Minor Collision Bumper Damage

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