The head injury criterion (HIC) is a measure of the likelihood of

head injury A head injury is any injury that results in trauma to the skull or brain. The terms ''traumatic brain injury'' and ''head injury'' are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of inju ...

arising from an impact. The HIC can be used to assess safety related to vehicles, personal protective gear, and sport equipment. Normally the variable is derived from the measurements of an accelerometer mounted at the

center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weight function, weighted relative position (vector), position of the d ...

of a

crash test dummy A crash test dummy, or simply dummy, is a full-scale Anthropomorphism, anthropomorphic test device (ATD) that simulates the dimensions, weight proportions and articulation of the human body during a traffic collision. Dummies are used by researc ...

’s head, when the dummy is exposed to crash forces. It is defined as:

\mathit\mathit\mathit =  \max_ \bigg\

where ''t''₁ and ''t''₂ are the initial and final times (in seconds) chosen to maximize HIC, and

acceleration In mechanics, acceleration is the Rate (mathematics), rate of change of the velocity of an object with respect to time. Acceleration is one of several components of kinematics, the study of motion. Accelerations are Euclidean vector, vector ...

''a'' is measured in ''g''s (

standard gravity The standard acceleration of gravity or standard acceleration of free fall, often called simply standard gravity and denoted by or , is the nominal gravitational acceleration of an object in a vacuum near the surface of the Earth. It is a constant ...

acceleration). The time duration, ''t''₂ – ''t''₁, is limited to a maximum value of 36 ms, usually 15 ms. This means that the HIC includes the effects of head acceleration and the duration of the acceleration. Large accelerations may be tolerated for very short times. At a HIC of 1000, there is an 18% probability of a severe head injury, a 55% probability of a serious injury and a 90% probability of a moderate head injury to the average adult.

Automobile safety

HIC is used to determine the U.S.

National Highway Traffic Safety Administration The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation, focused on automobile safety regulations. NHTSA is charged with writing and enforcing Feder ...

(NHTSA) star rating for automobile safety and to determine ratings given by the

Insurance Institute for Highway Safety The Insurance Institute for Highway Safety and Highway Loss Data Institute (IIHS-HLDI) is an American nonprofit organization. It was established in 1959, and it is noted for its safety reviews of vehicles in various simulated traffic situations, ...

. According to the

, head injury risk is evaluated mainly on the basis of head injury criterion. A value of 700 is the maximum allowed under the provisions of the U.S. advanced airbag regulation (NHTSA, 2000) and is the maximum score for an "acceptable" IIHS rating for a particular vehicle. A HIC-15 (meaning a measure of impact over 15 milliseconds) of 700 is estimated to represent a 5 percent risk of a severe injury (Mertz et al., 1997). A "severe" injury is one with a score of 4+ on the Abbreviated Injury Scale (AIS) Data for specific vehicles can be found on various automotive review websites. Some sample data is as follows, for comparative purposes: * The 1998

Ford Windstar The Ford Windstar (later the Ford Freestar and Mercury Monterey) is a minivan that was produced and sold by Ford Motor Company, Ford. The replacement for the Ford Aerostar, the Windstar adopted the front-wheel drive configuration of the Chrysle ...

, marketed as one of the safest minivans of that year, tested out to a HIC=305 score for driver * A small car, a 1998

Dodge Neon Dodge is an American brand of automobiles and a division of Stellantis, based in Auburn Hills, Michigan. Dodge vehicles have historically included performance cars, and for much of its existence, Dodge was Chrysler's mid-priced brand above Ply ...

, tested at HIC=265. * A common family sedan, a 1998

Toyota Camry The Toyota Camry (; Japanese: トヨタ・カムリ ''Toyota Kamuri'') is an automobile sold internationally by the Japanese auto manufacturer Toyota since 1982, spanning multiple generations. Originally compact in size (narrow-body), the Cam ...

, tested at HIC=288. * A 2007 Camry at HIC=175. A comprehensive searchable database of vehicles and their HIC scores is available a
safercar.gov

Athletics and recreation

Sport physiologists and

biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to Organ (anatomy), organs, Cell (biology), cells and cell organelles, using the methods of mechani ...

experts use the HIC in the research of safety equipment and guidelines for competitive sport and recreation. In one study,

concussion A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include headache, dizziness, difficulty with thinking and concentration, sleep disturbances, a brief ...

s were found to occur at HIC=250 in most athletes. Studies have been conducted in skiing and other sports to test adequacy of helmets

References

{{reflist

External links

Use of Head Injury Criterion in Crash Test RatingsInjury Measurements and CriteriaSaving Lives with Impact Protection Product
Automotive safety Neurotrauma Mathematical modeling

Automobile safety

Athletics and recreation

See also

References

External links