crash sci myths&realities of mc helmets

8/2/2019 Crash Sci Myths&Realities of MC Helmets

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The Myths and Realities of Motorcycle Helmets

y Dr. Voyko Banjac

Readers’ correspondence and discussion in Friction Zone in

the past few months, related to the proposed Idaho helmetlaw, opened up a number of interest-

ng topics. A major concern shared by

numerous readers (and riders) ishe likely infringement of such aaw on their personal choicend freedom, which is

nderstandable. However,s part of the discussion,

noticed several exag-erations, half-truths, and

ven outright nonsensepouted in the namef “scientific evidence,”

oth for and against hel-met usage. I believe it’s

high time that we set theecord straight. As riders, it’s

n our best interest to educateurselves as much as possiblebout all aspects of motorcycling

o that we can have the knowledge toide safely and enjoy our sport.

Here is a list of some of the controversial helmet-elated “facts” that seem to make the rounds. Within this article,

ve attempted to address each issue with just a brief explanation.n the next few months, I’ll address the most critical ones with a

more detailed analysis.

Myth 1: All Helmets Are Made Essentially the SameNot true. Other than the obvious wide variety of styles, designs,

izes, etc, there are three major functional types of motorcycle

helmets: legal, DOT- and/or Snell-certified full-face (Figure 1);egal, DOT-certified half-face (Figure 2); and illegal, non-certified,novelty-type” (Figure 3). The difference in safety and protection

etween the three types is enormous. DOT- and Snell-certifiedhelmets are tested to stringent engineering standards to ensure

hey keep the impact forces below a certain tolerance level.

Novelty-type helmets are not intended for use as head proteand therefore do not conform to any safety standard.

Myth 2: Helmets Do More Harm than GoodNot true. There is absolutely no question whatsoever in

scientific community about the benefit of helmets. Studies ducted in the US, Europe, and Asia over the past 50 years

consistently validated the injury-reducing qualities of helmScientists have not

done testing but have analyzed thousands of life crashes to determine

effect of helmets on severity of injury. Although no helmet can a

lutely eliminate all chance of injury, if yoabout to get into an accident you’re many t

more likely to survive wearing a quality hethan not wearing one.

Myth 3: Published Studies Show that Helmets Unsafe

Theoretically true, but deceptive. In this dayage, anyone can “publish” anything they w

A quick Google search will reveal web and even books that claim the earth isElvis is alive, the president is an alien ro

and similar nonsense. The true test of any sis its acceptance by the scientific commu

Criteria such as author’s credentials, refererelied on, and scientific accuracy of calculation

all used to gauge the credibility of studies. To daterecognized scientific society has accepted the blanket argumthat helmets are unsafe. There are indeed non-scientific, pop

based articles that attempt to prove helmets are unsafe, but

(if not all) of those have been critiqued and proven false duincorrect physics, misinterpretation of reference data, or biasubjective methodology.

Myth 4: A Helmet Can Cause Injury to the Neck or EvenHead Itself

Partially true, but deceptive. Given the right hit at the right ato the right part of the body, virtually anything can cause in

Yes, a poor-quality helmet can fracture in an impact and the japieces can penetrate the head. A worn visor can crack and p

Reprinted from June 2006 Friction Zone is a monthly motorcycle maga

>> PA

C R A S H S C I E N C E

Figure 1This DOT-certified full-facehelmet provides the best

head and face protection.

Reprinted with permission from Friction Zone, 60166 Hop Patch Spring Road, Mountain Center, CA 92561.



ut an eye. The back part of a helmet can, under just the right cir-

umstance (like when a rider falls on his back and hyper-extendshis head) act as a fulcrum and injure the cervical vertebrae orven the spinal cord. However, these types of

njuries are so rare that it would be foolisho focus on them and ignore the much

more likely, and much more injuri-us, “head bonk” which causeshe vast majority of injuries and

atalities (brain injury, concus-ion, skull fractures, hemor-

hages, etc.).

Myth 5: Helmets are Designed

o Pass Laboratory Tests, notReal-Life Accidents

Not true. In order to sell ahelmet, manufacturers have

o meet DOT testing criteria.Thus, before a new model is put out to market, it is tested in

laboratory to make sure it meets those criteria. Not only that,ut the DOT itself randomly checks helmets for

ompliance and can censure manufacturerswhose helmets do not meet the neces-ary standards. This is good for rid-

rs, because it allows us to comparepples to apples when shopping for

helmets rather than have to rely ondubious marketing and advertising

ploys. The test criteria themselvesctually stem from more than 50ears of accident investigation

nd head injury research, so’s nonsense to claim that just

ecause they are tested in aaboratory, helmets have no real-life application.

Myth 6: A Five-Pound Helmet, at 60 mph, Becomes a 300-PoundObject on Impact

Absolutely not true. As a matter of fact, this statement has somany errors that one could write a whole book just critiquing it.

irst of all, the physics is wrong: force is not equal to mass timespeed. Second, even the units don’t balance out: “pounds-force”

s not equal to “pounds-mass” times “miles per hour.” Third, itdoesn’t account for the stiffness of whatever the object is hit-ng—the same object, at the same speed, suffers very different

orces if it hits a bush vs. a brick wall. Fourth, it doesn’t accountor the stiffness of the object itself. Throw a five-pound pillow

s. a five-pound brick at someone. Which hits harder? Fifth,

the significance of a “300-pound object” is questionable—is

static or dynamic load? How long of a duration? Spread out what area? Depending on the circumstances, a 300-pound ocan cause anything from benign short-term discomfo

near-fatal, long-term trauma. For years I have been ing that this rid

lous statement wfinally die awayit still seems to

regurgitated enow and again.

Myth 7: A Helmet is Designed to OProtect Us Up to A 13 mph Impact Spee

Partially true, but deceptive. The 13 mph valuindeed the impact speed at which helmets are tested, accor

to the DOT standard. However, this value wasn’t chosen as bthe “upper speed limit” of protection. It is the physical resu

the chosen six-foot drop height. The six-foot height stems the 90th percentile (i.e., 90% likely) accident type identified by

Hurt Report of 1981, and verified numerous times since. In 90more of real-life motorcycle accidents, the rider su

a blow to the by falling off bike from app

mately a six-fooing height, thus

ting the grounapproximately 13 mph. This impact sp

holds true regardless of the cruspeed of the motorcycle.

Myth 8: It is Impossible to DesiHelmet to Protect the Head at High Speeds

Not true. From a physics standpoint, designing a tective device such as a helmet is a fairly straightforward

Starting with an anticipated impact speed and an impact sur we can calculate the impact energy and stiffness. Then, selean injury threshold, we can determine the design specificat

of the helmet. In simple terms, impact energy depends onsquare of the impact speed. Impact attenuation thickness

the other hand, varies as the square-root of the impact eneTherefore, to a first approximation, an X times greater im

speed requires a helmet that is X times thicker. For exampthe current DOT standard results in helmet thicknesses oinches to protect against a 13 mph impact, to protect again

100 mph impact, we would need

100mph x1.5inches=11.5inches 13mph

Reprinted from Friction Zone • June 2006

Figure 2

This DOT-certified half helmetprotects most of your head

but leaves your face vulner-able to injury.

Figure 3

This novelty helmet is notdesigned to protect yourhead. It’s only purposeis as eye candy.

C R A S H S C I E N C E


>> PA




Reprinted from Friction Zone • June 2006

C R A S H S C I E N C

r about a foot of helmet thickness. With today’s advanced

materials, making such a helmet would not be a problem; unfor-unately, selling it would be a different story, as I can’t imaginemany riders willing to sacrifice looks for safety.

Myth 9: To Truly be Effective at 100 mph, A Helmet Would Haveo Be One Foot Thick

True, but deceptive. To maintain the same level of protection,nd assuming an impact into the same type of object (e.g., strong

and stiff), higher impact speed does indeed require a thi

helmet (as explained in the previous question). However, few head impacts actually occur at anything close to 100 meven if this were the actual pre-accident cruising speed. In

about 100% of cases, the rider loses control of his bike, falls dand hits his head on the pavement, and then continues to

(thereby scrubbing off speed) before finally hitting a roadobject. Thus, the primary concern would still be protectinghead from a six-foot (i.e., 13 mph) impact. FZ

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