Back in November of last year, the Insurance Institute for Highway Safety — better known as the IIHS — released its safety ratings for the all-new 2020 Subaru Legacy and Outback. The duo have long been considering among the safest cars on the road, capturing IIHS honors over and over again; the 2020 models were no different, each grabbing accolades from the independent safety-testing agency. Yet there was a slight disparity between the two models: while the Legacy received the top marks of Top Safety Pick+, the Outback only scored the penultimate rank of Top Safety Pick.
Which seemed a little odd, considering the Legacy and Outback are basically the exact same car.
Sure, the Legacy is a three-box sedan, while the Outback is a station wagon pretending to be an SUV. But apart from the added junk in the trunk and the lifted suspension, the two Subies are all but mechanically identical. They both use the same powertrain. They both are built off the same platform, boasting nearly identical wheelbases and widths. And, more importantly for the purposes of this conversation, they share the same headlights.
Yet the IIHS’s official announcement called out the Legacy’s optional curve-adaptive headlights as being the deciding factor in the TSP+ honor, even though those same lightblasters — which swivel in the direction the car is turning to throw their beams into the turn — also are offered on the Outback.
“While the 2019 Outback earned the higher-tier “plus” award, the 2020 model is limited to a Top Safety Pick due to an acceptable headlight rating,” the IIHS said by way of explanation. “That rating applies to its base headlights as well as its available curve-adaptive LEDs on models built after October 2019.”
Like any good journalists in this day and age, we turned to Twitter to seek more info. And surprisingly enough, IIHS responded.
Curious to know more, we wrote back asking if IIHS generally gave worse safety rankings to higher-mounted headlights than it did to low-riding ones — an idea that seemed a little counter-intuitive to us, considering basic physics means visibility should be improved with added height. We also asked about added details regarding the “glare” IIHS mentioned.
Thanks to the IIHS’s thoroughly, ridiculously comprehensive guide to its headlight testing procedures, we know that the agency says “the maximum glare for 5-10 [meters] should not exceed 10 lux” while “the glare illuminance for the remainder of the approach (i.e., 10-120 m for curves and 10-250 m for the straightaway) should not exceed the cumulative exposure distance limits shown in Figure 3.” (Figure 3, for what it’s worth, is the chart below.)
(“Lux,” in case you were wondering, is the standard unit of measurement for illumination. One lux equals one lumen of light per square meter; very roughly speaking, it’s the amount of light a candle would cast on a wall from a meter away, or a bit lighter than the ground would be on a clear night with a full moon.)
The 2020 Outback’s IIHS page, as well as the chart in the company’s tweet above, reveals that the low beams of the adaptive LED headlamps of the top-shelf Limited and Touring trims caused “some glare,” maxing out at 52.3% more than the suggested maximum at the left edge of a left turn from 250 meters (825 feet) away and 46.4% more than the limit from the right edge of a right turn from 150 meters (495 feet) away.
While the IIHS’s chart is a touch hard to decipher, as it seems somewhat outdated — the data points listed don’t correspond exactly to the distances mentioned in the Outback’s analysis — it seems to suggest that 0.5 lux is the glare cutoff for both of those aforementioned distances. Overages in the 50% range, therefore, would add up to an extra 0.25 lux — about the difference between the ground on a clear night with a quarter moon and a clear night with a full one.
So, that matter was a little more buttoned-up. Still, something about the test still seemed odd to us. We went back to Twitter once more, to find out a little about why the seemingly-arbitrary height of the test was chosen.
In other words: the Outback’s demerit, simply put, wasn’t because its headlights are worse for the driver, but because they’re worse for other drivers.
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