Police are warning they'll take a "zero tolerance" approach to motorists ignoring temporary speed restrictions during the Mohaka Bridge refurbishment.
A major works project involving the resurfacing of the "deck" of the bridge on State Highway 5 started last week.
Acting Senior Sergeant Clint Adamson said the 2-3 month job would involve occasionally reducing the highway down to a single lane.
"To ensure the safety of workers at the scene, and also recognising the importance of getting the bridge surface repaired in as timely a manner as possible, police will be taking a zero tolerance approach to anyone who ignores speed restrictions in the area," Mr Adamson said. "There will be delays and drivers need to plan ahead."
Speed was restricted to 30km/h, with a 24-hour traffic light system in place.
Members of the Commercial Vehicle Investigation Unit and highway patrol staff will be setting up regular checkpoints at the site over the course of the project, including early morning starts.
"I would also like to send a reminder out to drivers in general that the 4km/h tolerance normally in place over the holiday periods is extending throughout February."
An NZTA spokesperson said the project involved waterproofing the bridge's surface, before contractors would strengthen slabs. "This will extend the bridge's lifespan by approximately 15 years, as well as allow the bridge to accommodate heavier loads," the spokesperson said.