The Insurance Institute for Highway Safety (IIHS) has answered why the speed for its frontal crash tests is 40 mph, saying it comes down to real-world data and physics.

Raul Arbelaez, IIHS Vehicle Research Center vice president, said in a recent IIHS YouTube video that 40 mph “captures the middle of the distribution of real-world crashes where we know there are serious and severe injuries.”

“We know that there are crashes that are more severe, but we are capturing the bulk of the total number of crashes,” he said. “Most crashes are very low severity.”

Forty mph represents a crash when the vehicle is traveling at that speed and hitting a fixed object or another vehicle of the same weight also traveling at 40 mph. The three frontal crash tests are passenger-side small overlap, driver-side small overlap, and moderate overlap.

Consumers have also asked why IIHS doesn’t increase its test speed to 50 or 55 mph. IIHS said that has to do with crash energy.

“There are some unintended consequences that go along with that, including degraded safety in lower severity crashes because what happens is your vehicle ends up being stiffer in order to perform well in that higher severity crash,” Arbelaez said.

“Your crash energy increases exponentially with impact velocity, and so if we go from 40 miles per hour to 50, we’re looking at over 50% increase in crash energy.”

The moderate overlap is IIHS’ longest-running test, which was updated in 2022. It was updated to address a growing gap in the protection provided for front and rear occupants. In the first tests, only two out of 15 small SUVs, the Ford Escape and Volvo XC40, protect the rear occupant well enough to earn a good rating.

Last year’s biggest change was the replacement of the original side crash test with an updated version that uses a heavier barrier traveling at a higher speed. Initially, an “acceptable” or “good” rating was enough to garner the lower-tier Top Safety Pick award. This year, a “good” rating is required for either Top Safety Pick or Top Safety Pick+.

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Featured image: Raul Arbelaez, IIHS Vehicle Research Center vice president, speaks with IIHS Media Relations Director Joe Young in a recent YouTube video from the institute (Credit: IIHS)