Many passengers were unaware the Cronulla-Sutherland rail line would close this week for track work and other maintenance.
Sydney Trains arranged a fleet of privately owned buses to run between stations, with express services from some locations to and from the city.
The shutdown began last weekend and will continue until 2am this Monday (July 4).
Passengers were overheard complaining that they had not been forewarned.
Normally, the Leader is contacted by Sydney Trains, but no advice was given this time.
One unsympathetic bus marshal said people were "whingeing" about the lack of notice on Monday, the first weekday on which passengers were affected.
"I don't care, as long as they don't whinge at me, because I don't work for the railways," he told one passenger.
Sydney Trains said six complaints were received on its 131 500 line, and only one unhappy comment was made on Twitter.
A spokeswoman said Sydney Trains understood that replacing trains with buses ‘‘isn’t ideal for our customers, but it’s essential for providing the reliable service they expect’’.
She said advice about the shutdown had been provided through posters and brochures at affected stations
and on the Transport NSW social media ‘‘handles’’.
Track work alerts had been posted on the Sydney Trains website and announcements had been made on stations and trains.
The spokeswoman said the work, costing $5.2 million, included improvements and maintenance of drainage and rails, removing dangerous trees, maintaining signals and overhead wiring, and removing graffiti and litter.
‘‘We’re also painting and refurbishing the rail bridge at Gymea and installing new platform tiles at Miranda,’’ she said.
A bonus for passengers was that travel on the buses organised by Sydney Trains is free for those holding valid pass or ticket.
Also, some found the express bus services to and from the city during lighter school holiday traffic even quicker than the train.
A Sydney Trains spokesman said many buses did not have Opal card machines and it was not practical to issue tickets.
He said, while revenue was lost, ‘‘our priority during track work is to get passengers to their destination as quickly as possible’’.
Were you surprised by the line closure?