Traffic Light Thought–Corrections Van CAN numbers mean what?

For years I have seen Corrections NZ Prisoner transfer vans on the motorway heading North in the morning commuter traffic. They are distinctive and all have a prominent identification in the form of the letters CAN followed by a number. I’ve always wondered what the CAN indicated, an abbreviation?
Corrections ? ?
Could not figure it out and when I saw Corrections on Twitter asked them, sorted!
@robincapper Years ago this used to be an abbreviation for Chubb Auckland Northland - now it’s just used as a vehicle identification number.
— CorrectionsNZ (@CorrectionsNZ) August 27, 2018