What does DOT stand for?
DOT stands for Department of Transportation. This is the US government approved standard and the most popular helmet type in the country. DOT helmets are more shock absorbent and designed at protecting your skull from 90% of impact types. The maximum g-force allowed by the DOT test is 250g’s, though many helmets offer much more protection than the 250g limit. DOT helmets favorite shock absorbancy due to recent studies claiming that absorbing the force of an impact if more important than resisting it.
The Federal Motor Vehicle Safety Standard (FMVSS) known as FMVSS 218 (49CFR571.218), describes in great detail the requirements for "DOT" certification of all helmets sold in the United States for use by motorcyclists. Helmets that do not meet the minimal DOT certification standards may not be sold as "motorcycle helmets."
What Does DOT Certification Involve?
The Department of Transportation (DOT) standard is enforced by the National Highway Traffic Safety Administration (NHTSA.) In order for a motorcycle helmet to be DOT certified, it must conform to a few minimum requirements, and be able to pass a series of impact tests.
The impact tests are administered placing a headform (basically a dummy head equipped with measuring instruments) inside it to measure speed and g-forces as the helmet is dropped onto different surfaces from a pre-determined height. Based on the energy that gets transmitted to the head, the helmet is given a grade of pass or fail. Tests are done twice, to make sure the helmet can withstand multiple impacts in one crash.
Other tests are also done, such as a penetration test to make sure the head isn't impacted, and the retention system is also tested to make sure the helmet doesn't slide off in an accident.
The DOT Helmet Tests include:
- Helmet is dropped onto a spherical anvil from a height of 1.83m
- Helmet is dropped onto a flat anvil from a height of 1.83m
- Pointed striker is dropped onto helmet
- Weight is applied to retention system (up to 300 pounds of force for 120 seconds)
Links to part of our DOT testing results:
Most motorcycle helmet standards use impacts at speeds between 4–7 m/s (9–16 mph). While motorcyclists frequently ride at speeds higher than 20 m/s (45 mph), the perpendicular impact speed of the helmet is usually not the same as the road speed of the motorcycle, and the severity of the impact is determined not only by the speed of the head but also by the surface it hits and the angle of impact. Since the surface of the road is almost parallel to the direction a motorcyclist moves while driving, only a small component of their velocity is directed perpendicularly (though other surfaces may be perpendicular to the motorcyclist's velocity, such as trees, walls, and the sides of other vehicles). The severity of an impact is also influenced by the nature of the surface struck. The sheet metal wall of a car door may bend inwards to a depth of 7.5–10 cm (3.0–3.9 in) during a helmeted-head impact, allowing more stopping distance for the rider's head than the helmet itself. A perpendicular impact against a flat steel anvil at 5 m/s (11 mph) may be of approximate severity to an oblique impact against a concrete surface at 30 m/s (67 mph) or a perpendicular impact against a sheet metal car door or windscreen at 30 m/s. Since there is a wide range of severity in the impacts that could happen in a motorcycle accident, some will be more severe than the impacts used in the standard tests and some will be less.
If you are interested in the subject, here are some great articles to read up on: