Sydney Metro 'deeply apologises' after commuters stranded on trains

Sydney Metro has apologised after dozens of commuters were left stuck on immobilised trains for about one and a half hours on Monday afternoon.

Thousands of Sydney city commuters were met with major train delays during peak hour after the metro network stopped moving.

Sydney Metro confirmed three trains on the Northwest line were stuck from about 4.30pm until 6pm, blaming a "communication failure".

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About 180 customers were affected, according to the operator.

"Sydney Metro deeply apologises to customers affected by disruption to Sydney Metro Northwest this evening," it said, in a statement.

"The delays were not acceptable and a full investigation into the causes of the incident will be undertaken with service operator Metro Trains Sydney."

Transport Minister David Elliott said he expected the private operator to face contractual and financial penalties.

"While emergency replacement buses were provided, the delay in evacuating commuters was unacceptable," he said.

"I have directed Sydney Metro CEO, Peter Regan, to work with the private operator, MTS, to ensure the problem is avoided in the future."

Two trains were also stuck between Town Hall and Central for an hour about 6.30pm, an issue Sydney Trains blamed on congestion.

Transport for NSW confirmed trains ran late due to urgent track repairs at Town Hall Station and operational issues at Central Station earlier today.

Metro services were not running between Macquarie University and Castle Hill on the Metro North West Line due to a communications issue.

A spokesperson from the Transport Management Centre said replacement buses were organised "between Macquarie Park and Castle Hill in both directions."

"Metro services are still running between Chatswood and Macquarie University, and between Castle Hill and Tallawong," the spokesperson said.

"Anyone who needs to travel is advised to allow plenty of extra travel time, listen to announcements and check information displays for service updates."

The T2 line from the City to Parramatta and Leppington, the T3 line to Liverpool or Lidcombe via Bankstown and the T8 line to Macarthur via Sydney Airport or Sydenham were all significantly delayed.

These lines banked up, causing a flow-on effect through other parts of the network as well as creating mass amounts of congestion on platforms as swarms of people waited to get home.

For the latest public transport information, visit www.transportnsw.info.

Sydney Metro is expecting services to be back to normal by the morning peak.