Road safety data - Invercargill City 2010 - NZ Transport Agency

Explanatory notes for the appendix
1. Each traffic crash report has a diagram and a description of what happened. These are
used to classify the movements the vehicles were making when they crashed eg ‘collided
with parked vehicle’, or ‘lost control while overtaking’. In this report, crash types are
grouped into seven categories. The following page shows the types of crashes which are
included in each group.
2. Traffic crash reports also include information on why the crash occurred, or on factors
contributing to the crash. In this report the hundreds of contributing factor codes used by
New Zealand Transport Agency have been condensed into 16 groups for practical
reasons. Lists of the factor groups used in this report, and of all the contributing factors
used by New Zealand Transport Agency, are shown on the following pages.
3. Note that in the year 2000 there were some minor changes to the contributing factor
groups. The most significant change was that ‘inattention’ was grouped with ‘inadequate
check’ to form ‘poor observation’. This allowed a more accurate assessment of ‘fatigue’ as
a contributing factor, as it now has its own grouping.
4. The factor group ‘poor handling’ includes factor codes that were only introduced in 1998.
This could explain why there may have been a sudden change at this time.
5. The coding of the factors contributing to a crash is subjective. Therefore analysis using
contributing factor groups needs to be interpreted with caution. Also, to effectively target
safety or enforcement campaigns more analysis of the specific contributing factors
involved may be needed.
6. It should be noted that a traffic crash generally has more than one contributing factor.
Therefore, adding the number of crashes on graphs showing the number of crashes with
a given factor or factor group will be greater than the total number of crashes in the city
or district.
Appendix