What severity of injury should be expected from this type of impact? Did the roadway, vehicle and driver perform as expected? What about the post-impact consequences such as the vehicle fire? What were the factors that led to or contributed to the collision consequences? To answer such questions basic education is needed in many areas including how injuries are identified and classified.

The Abbreviated Injury Scale – or AIS – has long been used internationally for coding injury severities in all collisions. But it is not only useful for researchers. The public can get a much better appreciation of the risk of their death through understanding that certain injuries are more likely to lead to death than others.

The AIS was originally developed by American Association for Automotive Medicine (AAAM). That Association has changed its name to Association for the Advancement of Automotive Medicine. The AAAM as described the AIS as follows:

“The Abbreviated Injury Scale (AIS©) incorporates current medical terminology providing an internationally accepted tool for ranking injury severity. AIS is an anatomically based, consensus derived, global severity scoring system that classifies an individual injury by body region according to its relative severity on a 6 point scale (1=minor and 6=maximal). AIS is the basis for the Injury Severity Score (ISS) calculation of the multiply injured patient.”

As an example, superficial injuries such as cuts (lacerations), bruises (contusions) or scrapes (abrasions), may be coded as AIS=1 because the likelihood of death from such injuries is very low. Conversely the breakage of a thigh bone (fracture of a femur) may be coded as AIS=3 due to the higher likelihood that its complications could lead to death.

In 1974 Susan P. Baker (and associated authors) published a research paper entitled “The Injury Severity Score: Development and Potential Usefulness”. The Injury Severity Score (ISS) was defined as follows:

“An ‘Injury Severity Score’ was defined as the sum of the squares of the highest AIS grade in each of the three most severely injured areas. In illustration, a person with a laceration of the aorta (AIS=5), multiple closed long bone fractures (AIS=4), and retroperitoneal hemorrhage (AIS=3), would have an Injury Severity Score of 50 (25+16+9). The highest possible score for a person with trauma to a single area is 25. Use of the Injury Severity Score dramatically increased the correlation between severity of injury and mortality, as compared to using the AIS grade for the most severe injury.”

The AIS and ISS have been used by researchers for decades to describe collision injuries from all types of collisions, including pedestrian, motorcycle and all other events where humans have sustained injury.

So what does all this mean in practical, layman’s terms? Obviously, not all injuries are the same. Some injuries, such as decapitation (AIS=6) are currently untreatable and result in certain death. Yet the results of decapitation are not as monetarily significant as a lesser-severity injury to a spinal cord of a child resulting in quadriplegia and concentrated treatment throughout a prolonged lifetime. Those studying injury mitigation must sometimes make hard decisions about public safety with respect to creation of environments that reduce monetary costs or reduce the likelihood of death. The public may not recognize that the design of a transportation system must take into account the likelihood of certain types and severities of collisions.

For example, limited access freeways take away the likelihood of severe head-on collisions so that the severe injuries related to such occurrences are thus removed. Similarly vehicles are designed, not to prevent injury, but to channel those injuries into certain types that may be less expensive or less likely to cause death.

In the example of a side impact into a driver’s door, the interior of a door may be designed to be closer to the driver’s pelvis so that the door’s intrusion makes contact with a driver’s pelvic region early in the collision pulse. Thus the body’s lateral acceleration is commenced at an early time in the collision pulse. Meanwhile a side curtain air bag may reduce the likelihood that the driver’s head will move out through the side window and be struck by the edge of the hood of the striking vehicle. Yet some impacts into a driver’s door may produce such massive intrusion that even interior design and air bags may be sufficient. This is an instance where researchers and manufacturers must protect the occupant from the most common injury scenarios while accepting that a small number of scenarios may result in death.

The public needs to be aware that certain collision scenarios result in certain types and severities of injury. In some instances reported injuries do not match the collision scenario and those instances need to be revealed and investigated. As an example, the death of a driver of a passenger car that collides with the rear end of tractor-trailer should be suspicious if the collision appears to be of minor or moderate severity. When the front end of a car under-rides a trailer’s rear end there may not be proper engagement between the contacting surfaces such that the decision-making module controlling the car’s air bag may not initiate the deployment until a later time of contact. Meanwhile the driver’s body moves forward into the zone where the air bag is to deploy and an “Out-Of-Position” (OOP) injury occurs when the air bag deploys into the driver’s head and chest regions. Those responsible for the public’s safety may not be willing to report such an occurrence despite the danger of doing so. There are many instances where an unaware or uneducated public allows such instances to escape detection and the results only become known to the small, special-interest groups who must answer to those results.

Having some basic knowledge of injury severities and how injuries are coded can be of use to the general public. The AIS and the ISS are two internationally recognized coding schemes that, combined with other public knowledge, can be used to develop informed opinions about where road safety issues exist.

Uninformed opinions expressed due to emotional responses from observations of singular events can be damaging to road safety as a whole. The pressuring of politicians, members of road authorities or police to make changes to highway, vehicular or driver characteristics without basic knowledge of the consequences may have the reverse effect than what is intended.  The solution should not result in a discouragement of the public from expressing those opinions. Rather the solution should cause an improved education of that public through transparent discussions about what issues matter. Discussions in layman’s terms, even though not precisely accurate, may be helpful in attracting persons who might otherwise be discouraged by the technical jargon.