IIHS examined the effectiveness of seat belt alerts and gave grades of "good," "acceptable," "marginal" or "poor," the organization said Thursday. It evaluated the volume, duration and timing of the alerts.
To receive a "good" rating, a vehicle must generate a loud signal and visual alert that last at least 90 seconds when somebody in the front row is unbuckled and at least 30 seconds when a previously buckled second-row seat belt becomes undone.
IIHS said that only the Subaru Ascent and Subaru Forester earned a "good" rating.
The report said 12 of the 26 vehicles received a "poor" rating: the Audi Q3, Buick Encore, Chevrolet Equinox, Chevrolet Traverse, Ford Escape, Ford Explorer, Honda CR-V, Honda HR-V, Honda Pilot, Mitsubishi Eclipse Cross, Volkswagen Atlas and Volvo XC40.
Almost all of those vehicles fell short of the duration or sound level requirements, with alerts that were shorter than eight seconds or that were as little as 1 decibel louder than the ambient noise in the vehicle, IIHS said.
Five Hyundai Motor Co. and Nissan Motor Co. vehicles received "acceptable" ratings, meaning they only failed to meet the standards for the second-row alerts. Seven Jeep, Mazda Motor Co. and Toyota Motor Corp. vehicles received "marginal" ratings.
For all the "marginal" and some of the "poor" ratings, Harkey said the solution is a simple software adjustment to extend the duration of the audible chime and visual warning.
"Through our discussions with automakers, we expect that a lot of them will do that in the very near future," he said.
A previous IIHS study showed that more noticeable seat belt alerts increase use among those who do not regularly buckle up. Harkey said that making these changes could result in 1,500 fewer motor vehicle fatalities a year.