November 2008 Safety Thoughts

Helmet Testing

by Dave Hansen, Safety Officer

 

This month Iím going to cover a subject Iíve steered clear of during my tenure as Chapter Safety Officer.  That subject is helmets, and in particular helmet testing.

How a helmet works defines how it needs to be constructed.  This construction includes a hard outer shell that absorbs & distributes localized impacts to a larger surface.  This will prevent point of impact intrusion and absorb abrasion at the contact point.  Inside the helmet is a layer of energy absorbing material, typically expanded polystyrene or EPS.  Many times the EPS layer will be comprised of several different densities, joined together to provide improved performance from directional impacts.  Inside the EPS will be foam padding & fabric covering to provide fit & comfort for the wearer.

Within the industry, there are several testing standards referenced & recognized.  These include the DOT testing, which is really the Federal Motor Vehicle Safety Standard 218, the European testing standard ECE 22-05, the British testing standard BSI 6658, the Snell testing standard M2000/M2005 and American National Standards Institute or ANSI Z90.  For todayís discussion, Iíll be concentrating on the DOT standard vs the Snell standard.

The actual testing procedures for these two standards are similar, but conducted to differing parameters & specifications.  Because of the differing specifications in these standards, Snell approved helmets tend to be stiffer and subject the wearer to higher G loads during impact, while DOT helmets have more flex, are ďsofterĒ & have lower subjected G loads.  Common perception of these 2 standards generally is that the Snell standard is a tougher standard than the DOT standard and helmets that meet the Snell standard provide better protection than helmets that only meet the DOT standard. 

Recently published papers dispute this long-held belief based on results of clinical studies.  These clinical studies have shown that internal, permanent brain trauma can occur at G loads well below the higher limits imposed in the Snell standards, sometimes even lower than those specified in the DOT standard.

The good news here for us, the consumer, is that reputable helmet manufacturers are taking these clinical studies seriously and helmet design & protection have improved dramatically in the last several years.  Proof too, that these clinical studies are changing the industry is the fact that the Snell M2010 testing standards will be incorporating changes that will impose lower limits for loading G force exposure to the wearer.

Those interested in reading more about this can find info at this link:  

Blowing_the_Lid_Off.pdf

Additional Resources for DOT approved helmets:

http://www.nhtsa.dot.gov/cars/testing/comply/fmvss218/index.html