8 Ball In The Wind

Sunday, June 28, 2015

Helmet Impact Velocities Not What They Seem

DOT helmet test impacts & velocities

Take a look at the diagram above.  It shows the impact velocities that a DOT motorcycle helmet needs to attenuate in order to comply with the Federal Motor Vehicle Safety Standard 218.  Take a close look and think about what the image shows.  

FMVSS-218 requires two impacts onto a "spherical anvil" at a velocity of 11.62 mph.  That impact velocity is obtained by dropping the helmet from a height of 54.33 inches.  In real world equivalents; while you are sitting on your bike, at a stand still, fall over and strike your helmet on the curb.

FMVSS-218 also requires two impacts onto a "flat anvil" at a velocity of 13.4 mph.  That impact is obtained by dropping the helmet from a height of 72.05 inches above the "flat anvil".  In real world equivalents; you pull your helmet off the six foot high closet shelf, and it slips through your fingers, falling to the floor.

That is the extent of impact protection a DOT helmet is required to provide.  Yet an extremely high percentage fails to do so every year.  Part of the problem is that there is no requirement for helmet manufacturers to test their helmets prior to being allowed to "self-certify" that their helmets meet the requirements of FMVSS-218.  The DOT allows manufacturers, virtually all of whom are from outside the U.S., to "self-certify" that their helmets meet the standard with only the a "good faith belief" that their helmets would pass testing.  

In other words, the motorcycle helmets the legislature of Washington State forces motorcyclists to wear only depend on the "good faith belief" of foreign manufacturers that their helmets will indeed perform as required.  Only if the make and model of helmet is randomly chosen for testing by an independent laboratory, will it be known whether or not it actually meets the standard.  Between 1980 and 2008, over 61% of helmets that manufacturers had "self-certified" as meeting the DOT FMVSS-218 standard actually FAILED to do so.  Out of 1,540 helmet models tested during that period, 945 FAILED to meet the standard.

To quote Ed Becker from the SNELL Foundation; "Our standards call for impacts with a velocity of about 17.3 mph followed by a second impact at the same point on the helmet at about 14.8 mph.  A helmet that can take one of our headforms through these two impacts unscathed could probably* handle a single impact somewhat greater than 17.3 mph, but certainly no more than 23 mph.

DOT tests apply two impacts as well, both at around 13.4 mph, implying a single impact capacity greater than 13.4 mph, but certainly no more than 19 mph."

Those impact velocities do not take into account any forward velocity of the motorcycle.  If a fall from 72 inches (6 ft) equates to 13.4 mph, it would only require an increase to about 120 inches (10 ft) to reach the 19-23 mph that SNELL feels is the maximum impact velocity a motorcycle helmet is able to withstand.

Again quoting Ed Becker from SNELL; "Most head strikes are glancing blows.  The most common accident is the biker is thrown from the bike. falls to the road surface and scrubs off his cruising speed sliding along the roadway.  The impact velocity is not his cruising speed, but but just the downward component picked up in the fall."*

So, for glancing blows while "sliding along the roadway" helmets may be of benefit in protecting the head from abrasions and injuries attirbutable to "sliding along the roadway".  However, for direct impact velocites, helmets are recognized not to be nearly as effective.

To quote Professor Harry Hurt (author of probably the most in-depth traffic safety study of the 20th Century, the "Hurt Report"); "When impact speeds get up to 25-30 mph, there isn't a helmet in the world that is going to save you."

Washington State needs to join the majority of other states in the nation, and allow its citizens to exercise their right to choose for themselves what is the proper amount of protection for riding at any given time.  It does not mean you will always have to wear a helmet, or that you won't be allowed to wear a helmet.  Simply that each individual will be allowed to decide for themselves if they wish to wear a helmet on that particular ride, or not.  Think about it, and let your legislators know how you feel, with the facts to back up your statements.  I'll be posting more information in the coming weeks.  Together we can make a change in the way
we ride.

Catch ya on the road sometime...

* emphasis added by this writer to drive home the point being made in the statements provided.

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