The National Highway Safety Administration (NHTSA) has finalized a rule that updates two Federal Motor Vehicle Safety Standards connected to truck underrides.

The rule requires rear impact guards on trailers and semi-trailers with sufficient strength and energy absorption to protect occupants of passenger vehicles in multiple crash scenarios.

The NHTSA said the change would improve protection for drivers and passengers in light vehicles in the event of a rear underride crash.

But the Institute for Highway Safety (IIHS) has said in a statement the updated rule does not go far enough to be meaningful.

“For nearly 50 years, IIHS has pushed for stronger government regulations to improve rear underride guards on large trucks,” said IIHS President, David Harkey.

“While an updated standard went into effect in 1998, it was still too weak. Our research in the early 2000s confirmed that and showed that much more could be done to prevent underride. Building on our research and crash testing, we petitioned the federal government in 2011 to improve underride protection.

“The final rule issued by NHTSA on June 30 falls well short of addressing most of the concerns raised in our petition.

“While the new standard is an improvement over the old one, nearly all newly manufactured guards on trailers already meet this new standard, which is similar to a longstanding Canadian requirement.”

The IIHS said crash testing and the TOUGHGUARD award it inaugurated in 2017 had pushed the largest trailer manufacturers to strengthen their underride guards well beyond this level and demonstrated that further improvements were feasible.