The Insurance Institute for Highway Safety slapped each of the four minivans in the U.S. market with less than acceptable ratings in its new moderate front overlap crash test, which places a higher emphasis on back seat safety.

The Chrysler Pacifica, Kia Carnival and Toyota Sienna received IIHS’ “marginal” rating; the Honda Odyssey was rated “poor.”

The unfavorable ratings stem from adopting improved airbags and advanced seat belts in front seats while overlooking the second row, creating a “safety gap,” Joe Young, a spokesperson for IIHS, told Automotive News.

IIHS found that newer, advanced airbags and restraints are “rarely available” in the back.

“Back seat safety is important for all vehicles, but it’s especially vital for those, like minivans, that customers are choosing specifically to transport their families,” IIHS President David Harkey said in a statement.

While safety has improved in the front seats, there has been a comparative increase in the risk of fatal injury for belted, second-row passengers, according to research conducted by IIHS.

IIHS updated its test last year after it discovered the finding. The new test represents the first time the agency has used a dummy in the back seat to test frontal crash safety.

Automakers have done a good job with improved frontal airbags and more sophisticated restraint systems in the front but may not have been doing internal testing to find opportunities to enhance second-row safety, Young said.

IIHS is confident automakers will take note and make the changes quickly, he said, as most updates will not require structural alterations to the vehicle.

The Carnival and Odyssey are expected to undergo a freshening in 2024, which would provide opportunity for the automakers to enhance safety in the second row. That’s also the case for the Sienna, which is slated for a freshening in 2025. The segment’s top-selling Pacifica is unlikely to receive incremental changes as an all-electric version of the minivan in 2028 is likely.

Even with the new developments, IIHS said the back seat is still the safest place for children, who can be injured when front airbags inflate. Additionally, the rating does not apply to children secured properly in car seats.

Kia America spokesman James Bell said the automaker will “carefully evaluate the results … as part of its commitment to continuous improvement in occupant protection” but maintained that all Kia vehicles sold in the U.S. “meet or exceed” federal motor vehicle safety standards.

“Occupant protection is complex and involves a diverse range of variables, and Kia is proud of its strong safety record and integrity of its products,” Bell said.

Eric Mayne, a spokesman for Stellantis, said the automaker “routinely considers third-party ratings and factors them into our product-development process, as appropriate.”

Mayne also said that all of Stellantis’ models meet or exceed federal safety standards and that no single test determines vehicle safety.

Honda spokesperson Chris Martin said that the new IIHS test was performed on models that have not had a chance to be updated to align with the more rigorous back seat standards.

Martin said that the redesigned 2023 Accord was the only sedan of seven to receive a “good” rating in all rear passenger injury measures.

A spokesperson from Toyota declined to comment on the test results.

For a vehicle to earn a good rating, the test dummy — which is the size of a small woman or 12-year-old child and is situated behind the driver — cannot signal excessive risk of injury to the head, neck, chest or thigh.

All four minivans offer good protection in the front seat, but each has multiple issues when it comes to the second row, according to IIHS.

Jessica Jermakian, IIHS vice president of vehicle research, said the second-row occupant is vulnerable to chest injuries in all four vehicles because of excessive belt forces or poor belt positioning.

Those injuries, Jermakian said, can be life-threatening.

All minivans but the Sienna also lack seat belt reminders for the second-row seats, as IIHS highlighted in February.