The Snell Memorial Foundation began with good intentions, developing a new standard for helmet safety which went above and beyond that of the Department of Transportation’s outmoded test. The standard for motorcycle helmets has been based on the standard for automobile helmets since the start, despite the two disciplines crashing in very different ways. The test requires a two-impact hit in the same location, which seems far more likely in a car with a roll cage than a motorcycle where the rider can bounce every which way from Sunday. And a change to Snell’s testing formula just rendered its rating system for motorcycle helmets functionally useless.
ECE and FIM have developed a rotational way of testing helmets, which sees the lid crashed in six axes more in keeping with real world situations. This type of testing has required manufacturers to build softer helmets that deform more to lessen brain trauma. Snell has kept its double-crash standard intact, which rewards a harder helmet shell. Obviously the European standards don’t quite mate up with the American standards, and it has come to a point where manufacturers were forced to choose between the two ideologies.
In order to keep the Snell foundation logo on helmets which meet ECE and FIM standards, Snell simply made a second standard, which deletes the second hit but adds none of the rotational damage mitigation testing that ECE and FIM have developed. M2020D-rated helmets still see the double-bounce hard-shell test that it has always required, but M2020R helmets only require one hit to pass, the same first hit that ECE/FIM require. And to make matters worse, the D and R suffix might have a different decal on the inside of the helmet, but both get the same Snell logo on the outside! So it is now entirely possible to build a shitty hard helmet built to garbage DOT standards and still get a Snell rating! This is the opposite of progress in safety.
So in order to make sure Snell can sell its testing to more companies, which were looking likely to abandon Snell for ECE or FIM (or both), the foundation just compromised its value as a standard setting operation. The SA-rated helmets still appear to be tested in a functional and worthy capacity for four-wheeled motorsport, but until the foundation updates to a new standard more in line with ECE/FIM, that logo on the back of your noggin is practically useless.