Everything You Always Wanted To Know About Off-Road Motorcycle Helmets*

The DOT standard is the only mandatory standard in the U.S. Broken down into simple English, it includes tests for shock absorption, penetration resistance and strap strength. There is no test of the chin bar whatsoever. The next, and possibly the most controversial, has been the Snell M2005 standard which includes a chin bar test and higher energy (at higher speed) tests. That is largely for two reasons, the first being the higher impacts the helmet must take and still never transmit a deceleration of over 300G. M2005 is interestingly enough changing in the very near future to the M2010 standard with different (lower) peak levels and different weights for various sized headforms, bringing it more in line with current ECE 22-05 protocol and making it possible for Snell helmets also to pass ECE tests, something that is a bit of a problem with the M2005 standard helmets. The second issue, and something that we have concern over, is the need for a double impact test on a single location, particularly a severe impact. It is a very hard test to pass, and the likelihood of an off-road helmet having to absorb a severe impact in the same location during the same crash event is very slim. Remember, your helmet is a disposable piece of safety equipment, and such a test might imply that you can use your helmet after a good impact and expect it to work a second time. In the Snell Foundation's defense, it claims the second impact is a way to test helmets to a higher standard and works in place of an even more catastrophic single hit. The second hit also makes it difficult for some materials, like some lesser quality plastics and polycarbonates, to slip through.

What did we learn? The chart of the helmet impact results shows some pretty interesting findings. First, shell material is not nearly as important as the internal energy-absorbing material in most impacts. This is illustrated by the foam density samplings versus the rankings. Most all were EPS (Expanded Polystyrene), and there were some tricks and different methods going on inside a lot of these helmets to absorb impacts. Many EPS liners use multiple densities (harder = stiffer = higher density), and altering the location of the varying EPS densities makes a difference. Since a lot of these helmets are shooting to pass a well-known and established test, proper placement of foam density can be an art. But knowing that art we could have, if we had desired, also tricked or complemented the results in choosing our strike points. The impact locations we chose were not based on the known standards we have available, but were all within the areas covered by the standards.

So what do all the numbers mean? Well, the most difficult thing about understanding how to protect a head is how complicated it gets. Even the experts in head injury and standard development don't have all the answers yet. Differentiating between a laboratory-style impact (straight on, to a dead stop with a rebound) and a real-world impact that involves more of a glancing hit and some degree of rotational accelerations is the first step in confusion. Our tests isolate the vertical component. The NFL has spent millions of dollars re-creating impacts in labs using footage shot from different angles and examining helmets from players who were concussed. There is a difference in the types of injuries you might sustain inside of a helmet. The most important thing you need to understand is that protecting the brain is job one, and a force the brain does not like is the rotational force and related accelerations. There is the debate between which is more important to protect from: linear acceleration and deceleration or rotational acceleration. All humans respond differently to the sudden jerk and slowing of brain matter, and placing a G-load figure on that is difficult. About the closest I could find to a study assigning a G value to a concussion was a study done for European football (soccer) where it said that 50 percent of the time an 80G impact produced a concussion. The limit placed on most motorcycle helmets is 300G because it is likely levels above that could cause catastrophic brain injury. Further confusion is introduced since a rigid laboratory headform is not at all like a real soft and fleshy human head. The test headform's job is to isolate the performance of the helmet.

For the most part, it would be simple to say no matter what, lower Gs received by the head in a crash are a better thing. And for any particular crash, this is correct. But what you are asking a helmet to do is manage energy, and technically speaking each helmet has a finite ability to manage a certain amount of energy. The more catastrophic the impact is, the more energy that needs to be blown off, all in a very short space and in a very short time. Dealing with higher and higher level impacts takes a stiffer energy-absorbing material(s) and a stronger shell. Both of those things typically transmit higher Gs in a less severe impact. Just as a similarly "softer" helmet would fail sooner as the force becomes higher. It becomes an argument of lower Gs versus high level energy management. And typically the standards predict how a helmet will perform.

So how hard do you hit your head when you crash at 20 mph, or when crashing over a jump? Or when you tumble in the desert at 50 mph? Or when you smack a tree in the forest? What happens when you go down in the first turn and a footpeg hits your helmet? Most of the time our crashes are no worse than falling straight to the ground from a standing position, without breaking your fall, and hitting your head. The force your helmet deals with has a lot to do with the deflection of the helmet. It has a lot to do with other parts of your body hitting the ground first and helping to break the fall. That is why some of the crazy accidents you hear about are that way. Crazy. Stories like walking away from the 60-mph get-off or, conversely, someone who doesn't wake up when tipping over at 10 mph give you a clue to the unpredictability of crashing and how your head reacts to impacts.

What our test did was to isolate the vertical head impact to draw comparisons between different helmets. It was also done to see if there were variances in the way different surfaces acted on the helmets, and how different helmets compared to each other. It attempted to eliminate complications so we could make comparisons between helmet A and B.