On Friday, the National Highway Traffic Safety Administration denied a General Motors request that's likely going to result in the automaker recalling hundreds of thousands of SUVs over headlights that could cause glare to other drivers, according to Reuters. Specifically, 726,959 GMC Terrains from model years 2010 to 2017—or basically, every Terrain sold over the model's first-generation if the sales figures from Good Car Bad Car are to be believed.
According to the documentation, GMC discovered that its last-gen Terrain headlights did not fully comply with FMVSS No. 108 (the Photometry section outlined in S10.15.6, to be specific) in May 2019. It then filed a petition with NHTSA the following month arguing that the issue was inconsequential, a bit like Lamborghini did with its Huracan headlight issue.
For the engineers in the crowd, here was GM's main justification: "The refection has no effect on vehicle safety for oncoming or surrounding vehicles. The narrow reflection in question does not create a safety risk for oncoming or surrounding drivers, due to the extreme angle of the reflection. This angle, 80 degrees outboard and 45 degrees upward from each lamp's optical axis, is far above the range where the reflection could cause glare for oncoming or surrounding drivers, including the industry-recognized “glare points” referenced in Table XIX of FMVSS No. 108 at the following ranges: 0.5° U-1.5° L to L, i° U-1.5° L to L, 0.5° U-1° R to R, 1.5° U-° R to R."
The automaker also argued that the too-bright reflection isn't visible from the Terrain driver's perspective either and that the part in question has subsequently been replaced by supplier Stanley with a new one with graining on the affected surfaces that prevents reflection. Also, the issue apparently does not affect the current-gen Terrain and GM is only aware of one single customer "inquiry" over the issue and zero related crashes or injuries.
But NHTSA wasn't having it. The federal agency agreed with GM on the point that the GMC Terrain driver is very likely unaffected but countered with the notion that "glare to other motorists driving in proximity" may indeed be possible under non-ideal weather conditions such as snow and fog. It also pointed out in its Denial of Petition that the Terrain's bright points came in at about 450 to 470 candela, exceeding NHTSA's maximum of 125 cd by more than triple. For context, a candela is a unit that measures luminous intensity where one candela is about as bright as one wax candle.
On Friday, GM reportedly said it would "review NHTSA’s decision and explore potential next steps," with those next steps very likely being a recall on all affected GMC Terrains. This would involve informing owners and arranging for them to have the headlight parts replaced free of charge by a dealership.
NHTSA has been a bit busy correcting headlights lately. Between this and denying that similar request from Lamborghini, it also recently approved adaptive headlights for use on U.S. roads as a result of a bipartisan infrastructure bill.
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