To pass DOT testing, helmets...
To pass DOT testing, helmets such as this AGV, must adequately absorb impacts in the lab that are much harsher than those the rider is likely to experience in a crash on the street.
One widely circulated rumor is that the United States Department of Transportation (DOT) does not perform any testing of motorcycle helmets certified to meet Federal Motor Vehicle Safety Standard 218, better known as the "DOT standard." In fact, the National Highway Traffic Safety Administration (NHTSA, a division of the DOT) contracts independent labs to purchase motorcycle helmets from retail outlets and test them for compliance to the standard.
For 2005, 40 helmet models were tested. Of the helmets tested, 17 failed to meet the standards, but 10 of those just didn't fulfill the labeling requirements. (For example, the DOT label was too small or not in the designated place on the helmet.) Of the seven that failed the performance requirements, two were recalled.
More than 36,000 Helmet City HCI 100 and HCI 100G helmets were recalled under NHTSA Campaign No. 05E034000 because stitching could fail and allow the helmet to come off.
Almost 1200 of Advanced Carbon Composites's EXT-001 half-shell helmets were subjected to NHTSA Campaign No. 05E052000 because they failed to meet imact-attenuation, penetration and labeling standards.
None of the other five that failed to meet performance standards during testing were recalled. All except one failed the penetration test, which is generally considered less crucial than the impact-attenuation requirement. The Scorpion EXO-700 (which is also Snell-certified) failed both penetration and impact tests. The DOT apparently thinks the testing failured were not severe enough to recall these helmets.
More information can be found at the following sites: