Two of the most popular midsize SUVs in the U.S. are off to a "poor" start this summer.

Ford Motor Co.'s (F) - Get Report Ford Explorer and Fiat Chrysler Automobiles NV's (FCAU) - Get Report Jeep Grand Cherokee were given a "poor" rating in the latest round of crash tests by the Insurance Institute for Highway Safety, or IIHS.

The agency tested eight SUVs and rated them based on results from passenger-side small overlap tests. A small overlap crash occurs when the front corner of a vehicle hits another vehicle or object.

Three models, the 2019 Kia Sorento, the 2018 Volkswagen Atlas and the 2018 GMC Acadia, earned "good" ratings, and of the newly rated SUVs, the Sorento was the only one to earn the Institute's highest award, Top Safety Pick. Three others -- the 2018 Toyota Highlander, the 2018 Nissan Pathfinder and the 2018 Honda Pilot -- were rated "acceptable."

"Although some vehicles in this group offer very good protection, in other models, the airbags, safety belts and structure showed serious deficiencies," said IIHS Chief Research Officer David Zuby. "In those SUVs, a front-seat passenger would be at risk of injuries to the head, hip or leg in a right-side small overlap front crash."

The Ford Explorer received the agency's lowest rating after its structure was "seriously compromised," intruding by as much as 15 inches, during the passenger-side crash test.

"Measures taken from the dummy showed a high likelihood of injuries to the right hip in a real-world crash of the same severity, as well as a possibility of left lower leg injuries," IIHS said in its report.

The Explorer also had inferior structural performance in the driver-side test. The Ford midsize SUV, however, earned "good" ratings in other crash tests for the side, roof strength, head restraints and seats, as well as moderate overlap front.

"Customer safety continues to be one of our highest priorities when we design any of our vehicles and we continually make improvements to our vehicles to help our customers stay safe on the road," Ford said in a statement via email. "We fully expect next year's all-new 2020 Explorer will perform well on both [Small Overlap Rigid Barrier] test and other tests."

Still, the dismal rating comes after Ford announced it was largely shifting away from passenger cars -- except for the best-selling Mustang and the Focus Active crossover -- to focus on SUVs and pick-up trucks.

Unlike the Ford Explorer, the Jeep Grand Cherokee did not have structural issues, but it had other issues.

Source: Source: IIHS HLDIAction shot taken during the passenger-side small overlap frontal crash test.

"More alarming was what happened to the passenger dummy's head. It hit the dashboard hard through the front airbag and then, because the side curtain airbag didn't deploy and the door opened, it moved outside the vehicle during rebound," IIHS said. " Measures from the dummy indicated that right leg injuries would be likely in a crash of this severity and a head injury would be possible."

In response, FCA U.S. said, "All FCA U.S. vehicles meet or exceed federal safety standards. FCA U.S. vehicles are engineered to address real-world driving situations. No single test measures overall vehicle safety."

To this last point, FCA emphasized its "good" ratings from IIHS on four other crash tests, which happen to be the same tests the Explorer received "good" ratings for as well.

"The safety of a vehicle is defined by a wide range of factors, and independent safety ratings continue to be an invaluable resource for consumers," said Alistair Weaver, editor-in-chief at Edmunds, a Santa Monica, Calif.-based data provider that focuses on the auto industry. "It's critical that car shoppers include these ratings as part of their research process when considering the purchase of any vehicle."

Following the "poor" ratings, Ford shares rose 0.7% to $12.12 at 11:15 a.m. New York time, while Fiat Chrysler stock fell about 0.1% to $21.26.