Crash Analysis System (CAS) - differences in data between the current and previous system

The following information describes differences within the Crash Analysis System compared to the system prior to 20 February 2019.

For any clarification or further support, email cas.administrator@nzta.govt.nz

• Road curvature
• Vehicle type and vehicle usage
• Ethnicity
• Movement code changes
• Vehicle make and model fields
• Limited speed zone
• Additional surface condition
• Road markings
• Road feature
• Licence status

Road curvature

The existing values of ‘straight’ with three separate types of curvature have been rationalised down to simply straight or curved.

The existing curve variations will disappear from the system and be migrated into the new single curved value.

Vehicle type and vehicle use

In the previous version of CAS, the vehicle type field also included values that were really vehicle usage, such as taxi or school bus. A new vehicle usage field exists where these values can now be found.

The current list of vehicle types is:

The list of types of vehicle usage is:

Data that described taxis in the previous version of CAS now appears as vehicle type ‘car/wagon’ or vehicle type ‘van’ and vehicle usage as ‘taxi’. Vehicles described in the previous version of CAS as school buses now appear as vehicle type ‘bus’ with vehicle usage ‘school bus’.

User selection impact: When querying for school bus, taxi or rental, use vehicle usage field, not vehicle type.

Ethnicity

The Police have rationalised the ethnicity list. The main change is that specific Pacific Island entries for Fiji, Samoa, Cook Islands, etc. have been merged into a single general Pacific Islander category.

Previous ethnicity table

 Current ethnicity table

Movement code changes

The ‘lost control on bend’ row of movement codes (i.e. row ‘D’) has seen some expansion. The existing codes of ‘lost control on right-hand bend’ and ‘lost control on left-hand bend’, have been made more granular by each being given three variants: namely, finished up on road, finished up on left of road, and finished up on right of road. So where we used to have two choices we now have six. The ‘lost control at end of road’ code remains unchanged.

One issue is that, because the new variants on the existing codes are more granular, it is not possible to map old crashes into these new, more detailed, values meaningfully. To manage this, the original more generic ‘lost control on curves’ codes will be retained in the system, but no longer used for future crashes.

This may mean that when querying crashes that cover the changeover period you may need to use the old and new codes to get a complete picture, if that is the are you are investigating.

Vehicle movement codes [PDF, 3.5 MB]

Vehicle make and model fields

In the previous CAS, there was a free text field that contained a description of the make and model of the vehicle. There was no validation on this field, which resulted in such a large variation in spelling of standard vehicles that it could not be used for querying.

In the current system, the police officer selects the make, and then the model, from lists. i.e. two separate fields, with managed values. This ensures a consistency of reporting that allows this field to be used meaningfully in queries. For historical crashes, this will be less useful. The migration process has attempted to interpret the overall text present and split it into the new separate fields, with the objective of getting the vehicle make as accurate as possible and displaying the whole original text in the model field, to allow users a visual display of what was originally in place.

Limited speed zone

Limited speed zone (LSZ) used to be a valid speed limit, and some historical crashes have this value. During migration all these were changed to 50.

Additional surface condition

Previously one of ‘wet’, ‘dry’, ‘ice or snow’ was allowed as the base road surface condition. Currently there are also multiple ‘additional surface conditions’ allowed as follows:

• Slick
• Uneven
• Under maintenance
• Fuel
• Loose material
• Road edge issues

Road markings

Previously one of ‘pedestrian crossing’, ‘raised island’, ‘painted island’, ‘no pass Line’, ‘centre line’, ‘nil’ was allowed.

Now multiple road markings are allowed, each being one of the following types:

• Bus stop
• Centre line
• Flush median
• No passing line
• No stopping lines/signs
• Paint island
• Pedestrian crossing
• Raised island
• Turning bay
• Wide centre lines
• Nil

Road feature

Previously a road feature was one of ‘bridge’, ‘motorway ramp’, or ‘railway crossing’.

Now the list of road features is:

• Bridge
• Motorway ramp
• Railway crossing
• Tunnel
• Overpass
• Underpass
• Speed hump
• Tram lines
• Nil

Licence status

The previous licence status field was rationalised into separate licence type and licence status fields, as follows: