Sydney trains are on the move again after a communication failure saw the network grind to a halt.

The digital train radio system went down just before 3 pm causing all trains to stop until the issue could be resolved.

Transport New South Wales Chief Operations Officer Howard Collins has told Chris O’Keefe they’ve never had a failure of the digital train radio system like this before.

The cause of the outage is still under investigation, a failure of a physical piece of equipment is thought to be the most likely cause and there is no evidence at this stage to suggest it was a cyber attack.

See more highlights from Chris O’Keefe below:

Image: Nine