Hunter people travelling to and from Sydney by train from Friday will ride into the crunch of train cancellations across the Sydney network.
The cancellation of services until Sunday because of a pay dispute between the government and unions is expected to lead to strains on services.
The government says extra bus and other services would be rolled out over the three days, but the train shutdown would strain the capacity of replacement transport options.
People are being advised to alter their travel plans or allow for significant delays.