New crash tests show pickups with some of the oldest designs could struggle to protect passengers riding in the front seat.

The Insurance Institute for Highway Safety (IIHS) tested 11 mid-size and full-size pickups and found mixed results.

"In general, the pickup truck class of vehicles is not doing as good a job protecting right front passengers as other classes of vehicles," said David Zuby, IIHS' chief research officer.

Among the full-size pickups, the Ford F-150, the Ram 1500 and Nissan's Titan received the best possible rating of "good" — one grade above the Honda Ridgeline which was rated "acceptable."

By comparison, the IIHS said the Chevy Silverado 1500 and GMC Sierra provided "marginal" protection for passengers in the front seat when the right front corner of their truck slams into another vehicle or an object at 40 mph.

Dan Flores, a spokesperson for General Motors said the automaker is continually working to improve the safety of it trucks. "GM designs our vehicles to protect the occupants in a broad range of crashes including front, offset, angle, side and rear impacts," he said.

The IIHS gave a "poor" rating — the lowest possible — to the Toyota Tundra.

A spokesperson for Toyota told CNBC that "safety and reliability of its vehicles is a top priority." He added: "We'll continue to look for ways to improve in an effort to exceed customers' expectations — particularly in new testing such as IIHS' passenger-side front small overlap (tests) for pickup trucks."