New lane markings for the State Highway 29A Maungatapu roundabout are scheduled to be put in place next week.
The changes are being made by the New Zealand Transport Agency (NZTA) to help improve traffic flow and safety.
A new straight-through option to head towards the city will be added to the roundabout's centre lane for people travelling from Baypark.
NZTA portfolio manager Darryl Coalter said the straight-through option towards the city caused stacking of vehicles in the right-hand lane which ultimately caused a backlog at the roundabout.
"By giving motorists a second option to go straight-through we aim to improve the operation of the roundabout, making it safer for all users."
The lanes between the Maungatapu and Hairini roundabouts will also be tweaked to ensure motorists turning left into Welcome Bay Rd use the left-hand lane.
NZTA encouraged motorists to take extra care at the roundabout as people adjusted to the new layout.
The changes will be completed one night next week, weather dependant.
Traffic management will be in place during works – from 8pm to 5am the following day as the road is put down to one lane.