Members of the public will be able to walk or cycle through the Maungatapu underpass today, before it is opened to traffic.
The underpass will open temporarily as part of the Maungatapu Underpass Community Day, which is being held from 10am to 3pm. Food, refreshments, children's activities, local entertainment and prizes are available.
The underpass will open to traffic in mid-to-late June.
Once completed, it 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.