Validity of Police-Reported Information on Injury Severity for Those Hospitalized from Motor Vehicle Traffic Crashes

Abstract

Objective: The objective of this study was to assess the validity of police-reported information on the severity of injury for non-fatal motor vehicle traffic crashes (crashes) in New Zealand that resulted in hospitalization.

Methods: Details of crashes reported to the police resulting in non-fatal injury in New Zealand from January 2000 to December 2004 were obtained from Land Transport New Zealand Traffic crash reports (crash reports). Data about individuals' injuries were matched to New Zealand Health Information Service hospital discharge data. A severity score was assigned to the hospital International Classification of Diseases-10 (ICD-10) diagnosis codes, using a threat-to-life tool, the ICD-based Injury Severity Score (ICISS).

Results: Of the linked data, 49.3 percent of crash victims were recorded by police as having “serious” injuries on the crash report but given the police definition of serious injury, all 14,869 records should have been recorded as serious on the crash report. Of these, only 48 percent had an injury with a significant threat to life. Fifteen percent of those with a “minor” injury on the crash report had an injury with a significant threat to life.

Conclusions: The subjective police assessment of severity of injury was discordant in many instances with an objective measure of severity. There was variation in the concordance by personal, vehicle, and crash variables. This has implications for interpreting New Zealand's road safety statistics, the assessment of road safety programs, and the allocation of funding to target specific road safety problems.

Keywords:

• Severity
• ICISS
• Traffic
• Injury
• Police-reported crashes

ACKNOWLEDGEMENTS

This research was supported by a grant from the Road Safety Trust. G. McDonald was also supported by an endowment from the New Zealand Population Health Charitable Trust. The authors thank Daniel Russell for the data linkage and Colin Cryer for his helpful comments on an earlier draft of this article.

Notes

^aThis analysis assumes independence between the individuals involved in a crash, which is not true in all cases. However, preliminary analysis indicated that results taking into account the lack of independence were almost identical to the results that did not. This is presumably due to the fact that only 4.4% of the individuals in the dataset were from the same vehicle as another individual in the dataset. Only 26.1 percent of the individuals in the dataset were from the same crash as other individuals in the dataset.

¹ Accident severity is a crash-related variable recorded on the crash report that is defined by the worst injury sustained by an individual in that crash.