The Tinwald viaduct will be closed to vehicles until KiwiRail can repair an overhead beam that was damaged by an excavator being towed on a trailer a week ago.

There are concerns that another strike on the rail bridge before repairs can be made would result in significant structural damage.

The bridge remains safe for trains to use but the road below it (Melcombe Street) will be closed as a precautionary measure until repairs to the impact beam are made.

The temporary closure will be in place once traffic management plans for the closure are approved.

The bridge has a low clearance for vehicles travelling underneath it and a history of frequent strikes – 13 in the past five years. Engineers recommended the road beneath it be temporarily closed to motorists until repairs are made. A full road closure will be needed for the repair period; a timeframe for the work is not yet available.

Pedestrians and cyclists can still use the viaduct, but not vehicles - vehicles can cross the railway line at Compton Street, to the south. Signs alerting motorists to the temporary closure will be in place.