A new pedestrian bridge is forming under the cover of darkness at Pescara Point near Papakura.
The first piece of a structure that will stretch over the Southern Motorway was lifted into place in overnight work on Thursday.
A curved bridge will span 106m, connecting coastal paths beside the Manukau Harbour and Pahurehure Inlet, and also to local roadside footpaths.
NZ Transport Agency project delivery senior manager Andrew Thackwray says the heavy rain didn't hinder the first installation of the bridge section.
But he warned motorists to take care that they weren't distracted by the bridge taking shape and the extra activity around the work site.
"We advise drivers to keep their eyes on the road and watch their following distances when they're approaching Pescara Point, especially during the morning and afternoon peak travel times," he said.
The Southern Motorway (SH1) will be closed from 10pm until 5am between Papakura and Takanini Interchanges over several week nights.
Night-time drivers are advised to plan ahead, follow the detours and look out for closure reminders on overhead and electronic signs.
The work will take place under the stars as the motorway must be closed to allow for cranes to enter and safely lift the bridge supports and each section into place.
Designed to reflect the natural contour of the coastal environment nearby, the structure will let pedestrians and cyclists explore the new 4.5km shared-use path forming on the western side of the motorway, between the Papakura and Takanini interchanges.
Modelled after the tuna (eel), the structure will hover over 6m above the motorway traffic lanes.
The three other sections piecing together the bridge are expected to be installed shortly, with the next section to be added on next week, weather permitting.
The bridge is part of The Southern Corridor Improvements project, which covers the stretch of State Highway 1 from the SH20/SH1 connection at Manukau down to the Papakura interchange in the south.
Additional lanes in both directions and an upgraded Takanini Interchange will also be added. All additional motorway lanes are expected to be opened later this year.
Works on the bridge and on Great South Rd at the Takanini Interchange will continue into early next year.