This page provides a brief explanation of the source of the crash data used by engineers, researchers, road safety practitioners and policy makers in New Zealand.
Data collection process
Police attend, investigate and report road crashes.
The Police report on the crashes they attend, using a standard Traffic Crash Report (TCR) form, which includes information such as:
- the crash location
- the road environment
- the vehicles involved
- the vehicle drivers
- people injured or killed in the crash and the circumstances, including notes and a diagram indicating the movements of the vehicles involved.
Crash data stored in Crash Analysis System (CAS)
The crash reports are forwarded to expert coders at the NZ Transport Agency who code the details in the notes and diagrams of the TCR. Standard coding schemes are used to describe the movements of the vehicles involved in the crash and the factors that contributed to the crash. The coded data, along with scanned images of the original TCR form, are stored in the Crash Analysis System (CAS).
The investigation, reporting, coding and computerising of crashes take time, so there can be a delay of several months before crash data in CAS are complete.
For fatal crashes a brief preliminary report is provided by Police within 24 hours of the crash. This is less detailed but allows up-to-date tracking of road deaths.
Crashes, casualties, drivers
Published crash data can be reported from several different perspectives:
- Crashes - each crash event can be reported as a single incident, regardless of how many vehicles were involved or how many people were killed or injured.
- Casualties - there can be a number of people killed or injured in any one crash.
- Drivers/vehicles - there can be more than one driver or vehicle involved in any one crash.
It is important to be aware of these distinctions when reading published statistics, particularly when comparing reported statistics from different sources.