An overbridge in Auckland remains closed to traffic after cracks were found in it on Tuesday.
Contractors worked through the night adding structural support to the Remuera Road bridge in Newmarket.
The bridge is 100 years old. It has weak piers and is nearing the end of its working life.
But the rail line operator Ontrack says there's no danger of collapse.
However, road traffic is expected to be severely disrupted while the bridge is closed.
Trains are still able to pass under the bridge at a reduced speed of about 10km per hour. Only slight delays are expected for rail commuters.
The bridge is still open to pedestrians.