There's assurance scoping work on a second Auckland Harbour crossing is still under way, with plans expected mid-year.

Two Transport Agency reports have detailed defects in the 67 year-old bridge, and warn it's at risk of failure.

It says without long-term strengthening work, month-long lane closures, truck limits, and more wind-related restrictions are on the cards.

Chris Bishop says he won't be the Transport Minister who produces a pie-in-the sky idea that turns to custard.

He says they're taking an evidence led approach, engaging with the market, doing geotechnical assessments and extensive studies.

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