The twin bridges across the Waitaki River between Kurow and Hakataramea are being floodlit so scouring around a pier can be monitored and the bridges can stay open at night.
The bridges were to close on Saturday and Sunday nights, but the floodlighting, which was installed on Saturday, meant they could remain open.
New Zealand Transport Agency highways operation manager Peter Connors said the floodlighting would allow around-the-clock monitoring of the pier.
"This will continue, to see whether scouring around it back-fills with gravel from the river," he said.
The 131-year-old wooden bridges on State Highway 83 closed on Thursday and Friday nights between 8pm and 7am for safety reasons after the scouring was found.
Since then, a watch had been kept on the pier to see if the scouring would fill in.
"If this does not happen it may be necessary to underpin the pier, but a decision on that could be at least a week away.
"Another nearby pier was successfully underpinned recently," Mr Connors said.
