Two of the most popular midsize SUVs in the U.S. were given a "poor" rating in the latest round of crash tests that measure how well sport utility vehicles protect front-seat passengers in certain front-end collisions.

According to the Insurance Institute for Highway Safety, the 2018 Jeep Grand Cherokee and 2018 Ford Explorer had difficulty preventing some injuries when the front right corner of the vehicle collides with another vehicle or object while going 40 miles per hour.

"Somebody who is considering buying a brand new SUV, I would recommend that they choose something other than the Grand Cherokee or the Explorer," said Dave Zuby, senior vice president of vehicle research at Insurance Institute for Highway Safety. "There are clearly better choices out there especially if you are concerned about the safety of your family."

A "poor" rating is the lowest grade the IIHS gives during crash tests. It comes in below designations of "marginal," "acceptable" and "good," which is the highest rating awarded. In the latest crash tests of eight 2018 midsize SUVs, the Toyota Highlander, Nissan Pathfinder and Honda Pilot received overall ratings of "acceptable," while the Kia Sorento, Volkswagen Atlas and GMC Acadia were given overall ratings of "good."

"One of the things we observed is that the three good-rated vehicles are newer designs than the poor-rated Grand Cherokee and Ford Explorer," said Zuby. "Ford and Jeep are just behind in making the improvements that we would like to see."

IIHS rated Fiat Chrysler's Jeep Grand Cherokee as "poor" in protecting front seat passengers from lower-leg and foot injuries. During the safety organization's crash test, the side curtain did not deploy and the vehicle's door opened.

A spokesperson for Fiat Chrysler says, "All FCA US vehicles meet or exceed federal safety standards. FCA US vehicles are engineered to address real-world driving situations. No single test measures overall vehicle safety."

To drive home that point, FCA points out the Grand Cherokee has received good ratings from IIHS on four other crash tests.

It's a similar story for the 2018 Ford Explorer. The IIHS gives the SUV good ratings in four other crash tests, but in the most recent one, the agency gives the Explorer "poor" grades for the vehicle's structure and its ability to protect front-seat passengers from hip and thigh injuries in this particular crash.

"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," said Dan Barbossa, spokesperson for the Ford Motor. "We fully expect next year's all-new 2020 Explorer will perform well on both the small overlap test and other tests."

The IIHS admits it's hard to know how many fatal front-end collisions involve the passenger side front corner of the vehicle hitting another automobile or object. In 2016, almost 4,000 front-seat passengers were killed in auto accidents. That's just over 16 percent of all the people killed that year while riding in a vehicle.