The first section of the Sydney Metro Northwest skytrain to be built over a major road has been successfully completed.

“We’ve now reached another important milestone for Australia’s biggest public transport project,” Mr Constance said.

In a precision operation carried out over five nights, 12 segments of the skytrain were lifted over Memorial Avenue at Kellyville.

Each of the segments weighs about 84 tonnes and were lifted 11m into the air by the massive horizontal crane sitting above Memorial Avenue.

The segments were then attached and tensioned to form the deck of the skytrain, an elevated railway which will run 4km from Bella Vista to Rouse Hill.

“The skytrain span over Memorial Avenue has now been completed with minimal disruption to the road network.

“This construction method keeps traffic moving beneath the seven major roads and the T-way which the skytrain crosses, minimising impacts on drivers.

“When completed, people and vehicles will be able to freely move around underneath the skytrain, keeping the area connected.”

Once the skytrain is built, work will start on the elevated railway stations at Kellyville and Rouse Hill – two of the eight new metro stations.