ATLAS helmet's aren't SNELL certified, SNELL as a standard is good for Track use but not as good as ECE is when it comes to typical road use. The testing methods are largely the same e.g. they test similar impact points, they use steel anvils, and the weighted headforms are the same.
There are a few differences but actually Snell requires the helmet to be impacted twice on the testing anvil in the exact same spot of the helmet. Helmet safety standards should be based around what the majority of accidents are, and even in the case of the world of motorcycles the average crash speed at impact is only 21.5mph. Only 1/1000 crashes occur at 80mph + . If helmets were designed to manage impacts at such speeds , and designed to take an impact in the exact same place twice, then they would need to be extremely thick and have extremely dense EPS inside them to manage the energy of the impact.
Dense EPS is extremely hard, therefore if you fell off at a slow speed it would be like wearing a rock on your head because it wouldn't compress when you hit it with low energy.
This is why safety standards like SNELL are great for racers, but not at all optimum for casual riders / commuters.
There's an article to to find out more about the subject from 2017 if that's of interest. It’s because of this and the quotes within it that we decided to stick with ECE rather than SNELL http://www.mcrider.com/snell-motorcycle-helmet-certification-rated/