The NSW Government has announced that the Sydney Metro Northwest rail project is on target to be delivered at least $500 million under budget, with the final piece of track laid ahead of services starting in the first half of next year.

In a historic moment, the last section of 52.5 kilometres of railway tracks was installed at Bella Vista where the skytrain takes to the sky above the North West.

Over the past 22 months, 105 kilometres of steel rail was installed in the twin 15 kilometre tunnels between Bella Vista and Epping, on the 4 kilometre skytrain between Bella Vista and Rouse Hill, and at Sydney Metro HQ at Rouse Hill.

There were also 60,498 sleepers installed, 35,000 tonnes of ballast and 237,000 tonnes of concrete used in the track laying process alone.

On average, 300m of track was laid underground a week.