Sydney, Aug 19 (IANS): Sydney's new multi-billion-dollar driverless metro line officially opened to commuters on Monday.

The first passenger service on the Sydney Metro City Line departed Sydenham station in Sydney's inner western suburbs at 4:54 a.m. local time on Monday, travelling the 15.5 km tunnel under the central business district and Sydney harbour to arrive at Chatswood in the city's north shore at 5:16 a.m., Xinhua news agency reported.

Crowds queued from 1 a.m. local time on Monday to ride the first service on the extension of the existing driverless metro line, which was initially scheduled to open on August 4 but was postponed due to safety regulator approvals.

Trains will run every four minutes on the line during morning and evening peak periods, every five minutes in the middle of weekdays and every 10 minutes at night and on weekends.

The state government of New South Wales (NSW) estimates the service will carry up to 250,000 passengers on a typical weekday and save commuters travelling from Sydenham to Barangaroo in central Sydney 27 minutes.

Construction on the project began in 2017 and cost 21.6 billion Australian dollars ($14.4 billion), making it the largest public transport project in Australian history.

NSW's Transport Minister Jo Haylen said the opening of the line was a historic moment in the city's history.

Five new stations were built as part of the project and new platforms and entrances were added to the existing Central and Martin Place stations.

The existing stretch of the driverless metro line, which opened in 2019, stretches 36 km from Tallawong in north-western Sydney to Chatswood.

Once a final section is completed in 2025 the line will extend on from Sydenham to Bankstown in the city's south-west.