At certain times of day traffic is being limited to one lane on riverside Somme Parade.
Temporary traffic lights are being used for the short stretch between Cumbrae Place and Roberts Avenue.
They have been in place since late February, a Whanganui District Council spokeswoman said.
The limit to one lane is necessary so that repairs can be done to a dropout which happened during the June 2015 flood. It followed earlier dropouts and slumping at the site.
The repair work is progressing well, and is expected to be completed by the end of June.
The design and build contract for it was awarded to Whitaker Civil Engineering.
The council thanks motorists for their patience at the traffic lights, and reminds people to take care when travelling through worksites.