Head injury criterion
Encyclopedia
The Head Injury Criterion (HIC) is a measure of the likelihood of head injury
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 acceleration/time history of an accelerometer mounted at the centre of gravity of a dummy
’s head, when the dummy is exposed to crash forces.
It is defined as:
where t1 and t2 are the initial and final times (in seconds) of the interval during which HIC attains a maximum value, and acceleration
a is measured in g's (standard gravity
acceleration). Note also the maximum time duration of HIC, t2 - t1, is limited to a specific value, 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, one in six people will suffer a life-threatening injury to their brain (more accurately, 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).
(NHTSA) star rating for automobile safety and to determine ratings given by the Insurance Institute for Highway Safety
.
According to the Insurance Institute for Highway Safety
, 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 minimum 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) (Association for the Advancement of Automotive Medicine, 1990).
Data for specific vehicles can be found on various automotive review websites. Some sample data is as follows, for comparative purposes:
A comprehensive searchable database of vehicles and their HIC scores is available at safercar.gov.
experts use the HIC in the research of safety equipment and guidelines for competitive sport and recreation. In one study, concussions were found to occur at HIC=250 in most athletes. Studies have been conducted in skiing and other sports to test adequacy of helmets
Head injury
Head injury refers to trauma of the head. This may or may not include injury to the brain. However, the terms traumatic brain injury and head injury are often used interchangeably in medical literature....
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 acceleration/time history of an accelerometer mounted at the centre of gravity of a dummy
Crash test dummy
Crash test dummies are full-scale anthropomorphic test devices that simulate the dimensions, weight proportions and articulation of the human body, and are usually instrumented to record data about the dynamic behavior of the ATD in simulated vehicle impacts...
’s head, when the dummy is exposed to crash forces.
It is defined as:
where t1 and t2 are the initial and final times (in seconds) of the interval during which HIC attains a maximum value, and acceleration
Acceleration
In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...
a is measured in g's (standard gravity
Standard gravity
Standard gravity, or standard acceleration due to free fall, usually denoted by g0 or gn, is the nominal acceleration of an object in a vacuum near the surface of the Earth. It is defined as precisely , or about...
acceleration). Note also the maximum time duration of HIC, t2 - t1, is limited to a specific value, 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, one in six people will suffer a life-threatening injury to their brain (more accurately, 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 AdministrationNational Highway Traffic Safety Administration
The National Highway Traffic Safety Administration is an agency of the Executive Branch of the U.S. government, part of the Department of Transportation...
(NHTSA) star rating for automobile safety and to determine ratings given by the Insurance Institute for Highway Safety
Insurance Institute for Highway Safety
The Insurance Institute for Highway Safety is a U.S. non-profit organization funded by auto insurers, established in 1959 and headquartered in Arlington, Virginia. It works to reduce the number of motor vehicle crashes, and the rate of injuries and amount of property damage in the crashes that...
.
According to the Insurance Institute for Highway Safety
Insurance Institute for Highway Safety
The Insurance Institute for Highway Safety is a U.S. non-profit organization funded by auto insurers, established in 1959 and headquartered in Arlington, Virginia. It works to reduce the number of motor vehicle crashes, and the rate of injuries and amount of property damage in the crashes that...
, 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 minimum 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) (Association for the Advancement of Automotive Medicine, 1990).
Data for specific vehicles can be found on various automotive review websites. Some sample data is as follows, for comparative purposes:
- The 1998 Ford WindstarFord WindstarThe Ford Windstar is a minivan that was produced and sold by the Ford Motor Company from the 1995 to 2003 model years. This front-wheel drive minivan was the second minivan designed by the company, serving as a replacement for the rear-wheel drive Aerostar minivan. The two were sold concurrently...
, marketed as one of the safest minivans of that year, tested out to a HIC=353 score. - A small car, a 1998 Dodge NeonDodge NeonThe Plymouth/Dodge Neon, sold in Europe, Mexico, Canada, and elsewhere outside the United States as the Chrysler Neon, is a compact front wheel drive car introduced in January 1994 for the 1995 model year by Chrysler Corporation's Dodge and Plymouth brands...
, tested at HIC=655. - A common family sedan, a 1998 Toyota CamryToyota CamryThe Toyota Camry is a series of mid-size automobiles manufactured by Toyota since 1982, and sold in the majority of automotive markets throughout the world...
, tested at HIC=525. - A 2007 Camry also tested in the same range as the 1998 model, at HIC=505.
A comprehensive searchable database of vehicles and their HIC scores is available at safercar.gov.
Athletics and recreation
Sport physiologists and biomechanicsBiomechanics
Biomechanics is the application of mechanical principles to biological systems, such as humans, animals, plants, organs, and cells. Perhaps one of the best definitions was provided by Herbert Hatze in 1974: "Biomechanics is the study of the structure and function of biological systems by means of...
experts use the HIC in the research of safety equipment and guidelines for competitive sport and recreation. In one study, concussions were found to occur at HIC=250 in most athletes. Studies have been conducted in skiing and other sports to test adequacy of helmets
See also
- Automobile safetyAutomobile safetyAutomobile safety is the study and practice of vehicle design, construction, and equipment to minimize the occurrence and consequences of automobile accidents. Automobile safety is the study and practice of vehicle design, construction, and equipment to minimize the occurrence and consequences of...
- Crash testCrash testA crash test is a form of destructive testing usually performed in order to ensure safe design standards in crashworthiness and crash compatibility for various modes of transportation or related systems and components.- Types :...
- Sports injury
- Concussion
- Sport-related concussion
- Concussion grading systemsConcussion grading systemsConcussion grading systems are sets of criteria used in sports medicine to determine the severity, or grade, of a concussion, the mildest form of traumatic brain injury. At least 16 such systems exist, and there is little agreement among professionals about which is the best to use...