The Insurance Institute for Highway Safety has begun implementing tougher criteria for its safety awards. With the addition of a passenger-side crash test and revised criteria surrounding headlight ratings, just 15 vehicles qualify for the agency's top award.

To earn a 2018 Top Safety Pick+ award, vehicles must now earn a "Good" rating in headlight safety. Previously, they could get away with an "Acceptable" score in this category. Vehicles must also pass a new test that evaluates passenger-side protection in small overlap front crashes. Essentially, this is just like the driver's side small overlap test the agency has conducted for several years now. It replicates what happens when a vehicle's right corner crashes into an object or another vehicle at 40 mph.

Four small cars, three midsize cars, five large luxury cars, two midsize non-luxury SUVs, and one midsize luxury SUV qualify for the award. Minivans, pickups, and mini cars are absent from the list at this time. As the year progresses, IIHS will evaluate more vehicles.

Another 47 vehicles earned the regular Top Safety Pick award. To qualify for this honor, vehicles must now earn at least an "Acceptable" headlight rating. Here are the 2018 Top Safety Pick winners so far:

BMW 3 Series sedan

Hyundai Ioniq Hybrid

Hyundai Elantra GT

Mazda3

Mercedes-Benz GLE