How does the New Zealand Transport Agency rank bridges for replacement and what formula, if any, is used?

Answer

I am advised that NZTA does not maintain a single, national ranking of all state highway bridges for replacement, and there is no single formula that ranks every potential bridge replacement across the network. NZTA regularly inspects and monitors state highway bridges and it maintains an internal programme of candidate structures being considered through the End of Life renewal pathway. More information on how bridge replacements are considered by NZTA is available at: https://www.nzta.govt.nz/assets/planning/business-case-approach/docs/Bridge-replacement-at-end-of-life.pdf