Station platforms on the South Coast line will not need to be altered to fit the new $2.3 billion fleet of new intercity trains.
The new trains will go into service from 2019 and will run on the South Coast, Newcastle and Blue Mountains lines.
The trains will cause issues on the Blue Mountains line, because they are too wide and too long for some of the platforms.
There would be no need to alter stations or tracks on the South Coast line, a spokesman said.
“There are no issues with width as the South Coast Line is already able to accommodate medium gauge train sets,” a Transport for NSW spokesman said.
“The new intercity fleet trains will be the exact same length as the current Oscar sets.”
The government ordered 512 carriages last year from a South Korean consortium, and they will feature two-by-two seating and phone charging stations at each seat.
Transport for NSW said it had been clear about the need for modifications to the Blue Mountains line, which it said would bring this part of the track in line with the rest of the network.
The problems on the Blue Mountains line stems from the fact some platforms can only handle the ageing V-Set trains, which are just under three metres wide.
The new intercity fleet trains are 3.1 metres, too wide for these stations.
The stations will need to be altered and around 75 kilometres of line moved or replaced to allow the new trains to run.
Some stations will need to be lengthened so each carriage of the 10-car sets will fit alongside the platform.
This work is due to start later this year and is expected to take two years to complete.