How did the New Zealand Transport Agency calculate that the 114 year old Waihenga bridge outside Martinborough has a remaining lifespan of 20-30 years and what evidence, if any, does the agency have that confirms this calculation?

Answer

I am advised the current assumed 20-to-40-year remaining life for the Waihenga Bridge was not calculated using a simple age-based formula. Rather, it is based on NZTA’s asset management approach and informed by ongoing structural inspections, engineering assessments, and specialist technical advice on the condition and performance of the bridge. NZTA undertakes long term asset life and renewal forecasting to support portfolio planning. The actual remaining service life of an individual bridge depends on changing factors such as its condition, deterioration, loading, environmental exposure, maintenance, repairs and service requirements. These factors are monitored over time, and any bridge specific estimate may change as further inspections, investigations and maintenance are completed. The remaining life will continue to be reviewed and updated.