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On a recent trip around New Zealand, I noticed that many items of infrastructure on the highways are labelled not only with a name but with a number; see the two example photographs:

Friends Creek

McDonalds Bridge

I haven't seen a system like this being used in any other country although I am familiar with the idea of power companies numbering each power pole. I assume that the New Zealand numbers are unique and refer to a national infrastructure database of some kind but I have been unable to find any information about it at all. I should add that, although my two photographs both relate to bridges, they are not the only things that are numbered. Can anyone tell me how the numbers are used (e.g., search and rescue, infrastructure maintenance, etc) and what the national database is called?

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  • 1
    In germany, the trees near roads are numbered. Dec 22, 2023 at 2:05
  • In the UK, all rail bridges are numbered in some way.
    – Bib
    Dec 22, 2023 at 16:43

1 Answer 1

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The numbers you are looking at are part of the New Zealand Location referencing system, a "linear referencing system for its state highway network." The overall system is described in Part B of the document, and its applicability to bridges is described in Part E.

A "reference station" is surveyed approximately every 16km on each highway, and then:

All bridges, large culverts and tunnels are given structure numbers based on their approximate displacement, to the nearest 100 metres, from the preceding reference station (reference stations are 'benchmarks' along a highway, approximately every 16 kilometres).

For example:

  • RS 232 + 8.24km (232 + 8.24 = 240.24) = Bridge 2402
  • RS 232 + 11.56km (232 + 11.56 = 243.56) = Bridge 2436
  • RS 262 + 11.52km (262 + 11.52 = 273.52) = Bridge 2735

The structure numbers are unique for each state highway but can be replicated for different state highways.

Data about each bridge is stored in the bridge data system, a description of which is available publicly; however, the New Zealand government appears to consider the list of bridges itself to be sensitive and has at least once denied a request to make it public.

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  • This is, essentially, the same system used in the US. Every road designated "highway" or better has mile markers. Bridges, culverts, etc. will have their own marker post or sign attached to the structure indicating the distance (in fractional miles) from mile zero on that highway. A bridge may have a marker indicating 104.2 indicating that it is 2/10 of a mile beyond marker 104, or 104.2 miles from wherever that highway "starts". Makes perfect sense to me!
    – FreeMan
    Dec 22, 2023 at 14:51

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