The 10-car train was made up of a four-car and a six-car section with both sections equipped with crew cabs at either end.

A Transport for NSW spokeswoman said it was one of three New Intercity Fleet trains that were undergoing testing.

"Trains have been undergoing testing on the South Coast line since April this year, with 19 separate test runs to date and more planned over the coming months," the spokeswoman said.

"These are modern trains and the new technology on board means that they are unlike any other train currently operating on either the suburban or intercity networks.

"For this reason, it is crucial that each part of the train is thoroughly tested to ensure that it is performing as it is designed to, and meets all of our network and safety standards."

In May this year, the Mercury reported the New Intercity Fleet arrival date had been pushed back a year to 2022.

The spokeswoman said the plan was to see the first trains on the Newcastle and Central Coast line before the end of the year.

"A timeline for when the trains will start operating on the Blue Mountains and South Coast lines will be determined after more trains are delivered and further testing completed," she said.

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