Strengthening work is being carried out on the Whangaehu River Bridge near Whanganui, with temporary speed restrictions in place from May 7.
Road users travelling on State Highway 3 south of Whanganui will have to follow stop/go traffic management between 7.30am and 5.30pm, Monday to Friday, New Zealand Transport Agency Waka Kotahi (NZTA) said.
Traffic restrictions are expected to be in place for about seven weeks.
A reduced speed limit of 30km/h will be in place during daytime work hours, and delays of up to 10 minutes can be expected.