"Uninjured" occupants are part of many NASS-CDS safety analyses. However, the issue of precisely identifying "uninjured" persons in NASS-CDS is complex. There is no such severity code as "AIS-0". Neither the AIS-90 or NASS-93 manuals contain codes for persons whose medical records are examined and who have been found to have no codeable injuries. As a consequence, there is no such thing as "MAIS 0" defined by the AIS and as a result there is no way to query the NASS-CDS data on the NHTSA website for MAIS=0 injuries. The more appropriate statement about persons without AIS coding would be that the person either sustained no codeable NASS/AIS injuries, or was not coded at all. However, there is no data "flag" to identify which one is which.

This paper examines the approximately 90,000 vehicles in CDS from 1997 through 2007 and their occupants to illustrate the issues with identifying uninjured persons. More than 1/3 of these vehicles do not qualify under CDS rules for occupant coding. Therefore, AIS severity or MAIS codes cannot be used for the occupants of these vehicles, even if the codes appear in the data base as "blank" or "0". In addition, for the approximately 90,000 occupants who do qualify for AIS/NASS coding (1997 through 2007) 35% (32,000) occupants have no AIS/NASS codes. A data run that relies on the MAIS code in the occupant file, (not the injury file), (which may be blank or zero) may assume these 32,000 occupants are "uninjured" rather than having “no codeable injury. This may result in a substantial overestimate of actual occupants without injury. This can seriously impact evaluation of safety interventions. This paper identifies 5 occupant groups and several methods that can be used to help identify which of the 35% of occupants qualifying for AIS coding but without AIS codes are most likely to be uninjured. Issues created by using both the police KABCOU and AIS/NASS scales in mixed analyses to identify uninjured persons are also discussed. This paper is intended to be a general resource for researchers conducting safety analyses in NASS CDS that include uninjured persons.