The latest rules now require a 'good' headlight rating and validation of both driver- and passenger-side performance in the small-overlap test.

The list of Top Safety Pick Plus honorees has been slashed to just 15 models as the Insurance Institute for Highway Safety implements stricter qualification criteria for 2018.

The 2017 evaluations granted a TSP+ award to vehicles that earned mere 'acceptable' marks for headlight performance. The list now excludes anything below a 'good' rating. Some automakers are presumably scrambling to optimize their headlight designs for the IIHS test scenario and rejoin the honor roll.

The organization also introduced passenger-side small-overlap testing after finding evidence that some vehicles had received small-overlap structural strengthening only on the driver side. All small-overlap tests were initially performed on the driver side for consistency, however "the ultimate goal ... was symmetric protection."

The IIHS has since launched another series of small-overlap tests to verify that automakers are applying structural improvements to both sides.

"Drivers expect that their passengers, who are often family, will be protected just as well as they are," says IIHS president Adrian Lund. "Manufacturers have been taking this issue seriously since we first shed light on it, and we're confident that good small overlap protection will become the norm on the passenger side, just as it has on the driver side."

Nearly half of the 2018 TSP+ awards are held by Hyundai Motor Group, which includes Kia and Genesis. Subaru follows with four models, while Mercedes-Benz has two.

"All automakers now recognize the important role of safety in consumer choice, and they are increasingly receptive to working with our engineers to understand the next steps in keeping people from harm in motor vehicle crashes and to make real changes in their vehicle designs," Lund says.