The Kia Trailster concept car is unveiled during the media preview of the Chicago Auto Show at McCormick Place in Chicago, on Feb. 12, 2015. Sport utility vehicles are unstoppable and automakers hope to cash in on the boom with some updated models coming to this year's Chicago Auto Show. The Chicago Auto Show will be open to the public from Feb. 14 through Feb. 22. AP/Andrew A. Nelles

The Mitsubishi concept GC-PHEV full size plug-in hybrid SUV is seen on day 1 of the Chicago Auto Show Press Preview at McCormick Place on February 12, 2015 in Chicago, Illinois. Sport utility vehicles are unstoppable and automakers hope to cash in on the boom with some updated models coming to this year's Chicago Auto Show. Paul Warner/Getty Images

The 2016 Acura RDX is unveiled during the media preview of the Chicago Auto Show at McCormick Place in Chicago, on Feb. 12, 2015. One out of every three new vehicles Americans bought last year was an SUV, according to Kelley Blue Book. SUV sales rose 12 percent to more than 5.5 million. That was double the pace of the industry as a whole. AP/Andrew A. Nelles

An interior view of the 2016 Acura RDX during the media preview of the Chicago Auto Show at McCormick Place in Chicago, Feb. 12, 2015. Sport utility vehicles are unstoppable and automakers hope to cash in on the boom with some updated models coming to this year's Chicago Auto Show. AP/Andrew A. Nelles

The 2016 Honda Pilot is unveiled during the media preview of the Chicago Auto Show at McCormick Place in Chicago, on Feb. 12, 2015. One out of every three new vehicles Americans bought last year was an SUV, according to Kelley Blue Book. SUV sales rose 12 percent to more than 5.5 million. That was double the pace of the industry as a whole. AP/Andrew A. Nelles

The 2016 Chevrolet Equinox is unveiled during the media preview of the Chicago Auto Show at McCormick Place in Chicago, on Feb. 12, 2015. Sport utility vehicles are unstoppable and automakers hope to cash in on the boom with some updated models coming to this year's Chicago Auto Show. The Chicago Auto Show will be open to the public from Feb. 14 through Feb. 22. AP/Andrew A. Nelles