The Maungatapu underpass is nearly done, with a community day planned for late May.
The New Zealand Transport Agency is warning people to expect delays as work gets underway to connect the underpass to Welcome Bay Road.
There would be lane diversions, speed restrictions, unsealed surfaces, and off-peak and night works on Welcome Bay Road near Greenwood Park, as well as lane diversions, speed restrictions, night works and temporary pedestrian diversions on Awanui Place.
"We will do as much work as we can during the April school holidays and at night to minimise the impact on traffic, however there will be some delays during the day due to the speed restrictions."
The Hairini and Maungatapu roundabouts on SH29A would be resurfaced in mid-May, while work to connect the underpass to Turret Rd and Hairini St would start later that month.
On May 27 the agency will hold a community day giving people the opportunity to walk or cycle through the new underpass before it opens to traffic.
Once completed, the Maungatapu underpass will be a two-lane link underneath the Maungatapu roundabout, improving the traffic flow around the Maungatapu and Hairini roundabouts and separating state highway and local traffic.