A group of four minivans recently tested by the Insurance Institute for Highway Safety for protection in small overlap front crashes showed some of the worst possible outcomes for this type of crash, with only one vehicle performing acceptably.

The Nissan Quest, the Chrysler Town & Country and its twin, the Dodge Grand Caravan, all earned poor ratings.

READ: Minivan crash report study

The exception was the 2015 Toyota Sienna, which earned an acceptable rating. It joins the Honda Odyssey, which last year earned a good rating in the test, in the ranks of TOP SAFETY PICK+ winners.

"Minivans are popular among parents, a group that tends to be safety conscious, but we've only seen two so far that offer decent protection in small overlap crashes," says David Zuby, IIHS executive vice president and chief research officer.

In the small overlap test, which replicates what happens when the front corner of a vehicle collides with another vehicle or an object such as a tree or a utility pole, the crash forces bypass the vehicle's main energy-absorbing structure.

These crashes may be especially difficult for minivans to handle. That's because minivans are typically built on car platforms but are wider than cars. As a result, more of the vehicle is located outside the main structure. Minivans also are heavier than cars.