The last of 12 centre-span beams has been lifted into place on the new $24 million replacement bridge at Atiamuri, about 40km north of Lake Taupo.

The bridge, which will eventually form one of the country's key freight routes, lies about 75 metres upstream from the current bridge on State Highway 1.

NZ Transport Agency projects service manager Bryce Carter said progress on site had been "excellent" with the bridge on track to open in April next year.

Work on the replacement bridge began in November last year.

Mr Carter said the new bridge would improve safety along the section of SH1 as well as ensure ''route security''.

Replacing the 50-year-old Atiamuri Bridge has been given high priority by the Government, due to the limited life of the structure.

Freight is expected to increase up to 75 per cent over that part of SH1 in the next 25 years.

The new bridge allows for two 3.5m lanes and a shared pedestrian and cycle walkway.

A new northbound passing land will also be constructed, running between the SH30 intersection and Hatu Patu's Rock.

Mr Cater said the bulk of earthworks around the project was finished.

The next stage of the project was installing drainage for the new road's pavement foundation.

Native planting and seed mixes has also been applied to the slopes facing either side of, and under, the bridge.

* Time-lapse webcam footage of the bridge, plus project information can be found at nzta.govt.nz/projects/atiamuri-bridge

- © Fairfax NZ News