But the Jeep Grand Cherokee, Toyota 4Runner and Ford Explorer got ''marginal'' ratings, while the Kia Sorento, Mazda CX-9 and Honda Pilot all were rated ''poor.''
The ratings are based on six crash test measurements done by the institute. Only the Equinox and Terrain got ''good'' ratings in a front overlap crash that mimics what happens when a car's front corner collides with another vehicle or an object like a utility pole. In the test, 25 percent of a vehicle's front end on the driver's side strikes a rigid barrier at 40 mph (64 kph).
The test, instituted in 2012, is more difficult than the U.S. government's frontal crash test, in which a car strikes a rigid barrier head-on at 35 mph (56 kph). IIHS says hitting only part of the front end makes it harder for cars to manage the energy from a crash. The test ''continues to challenge manufacturers more than a year and a half after its introduction,'' the institute said in a statement.
The institute uses its crash test scores to prod automakers into adding safety devices or making their cars more crash-resistant.
The institute said the Equinox and Terrain, which are almost identical, were modified by GM in the new model year to strengthen their front structure and door-hinge pillars. In tests, the Equinox driver's space was well-maintained, and the crash dummy's movement was well-controlled, the institute said.
The institute changed its requirements for vehicles to get the ''Top Safety Pick-Plus'' designation this year. To earn that, vehicles must get ''good'' ratings in four crash tests, ''good'' or ''acceptable'' in the overlap test, and they must have available a front crash prevention system that either warns the driver of a crash or stops the vehicle with automatic braking.
Of the nine midsize SUVs, only the Equinox and Terrain and the Highlander qualified for ''Top Safety Pick-Plus.''
The Honda Pilot was the worst performer of the group, largely because the driver's space was seriously compromised in the overlap test, the institute said.
Honda said in a statement that with each redesign, the Pilot has been a leader in light-truck safety and driver-assist technologies ''and we are committed that it will continue to do so in the future.''