During Seniors Week in April, South Coast commuters noticed the usual pair of four-car trains that left Central just ahead of the evening peak had been turned into eight-car trains.

These two trains are the focal point for complaints over crowding on the South Coast line, with vestibules and stairs regularly occupied by commuters.

One commuter claimed to have sat in the toilet to avoid standing from Central to at least Sutherland.

The addition of the extra carriages for a few days surprised commuters, with some wondering why it couldn’t happen all the time.

READ MORE: Hundreds of complaints about crowded trains

Others claimed the extra carriages came from cancelled services though there had been no trains cancelled at that time.

Wollongong MP Paul Scully put a question without notice to Transport Minister Andrew Constance as to why these extra carriages were added.

“NSW Trainlink provided as much capacity as possible across its entire network for people attending the Premier's Gala Concerts on April 5 and 6, part of Seniors Festival 2018, by taking carriages out of their usual maintenance cycle to build up services,” Mr Constance said.

The Minister also said the adding of extra carriages was something that would not be happening on a regular basis.

“It is not possible to remove trains from the maintenance cycle permanently and still maintain a safe and reliable train service,” Mr Constance said.

READ MORE: No space for more trains, says report

That carriages were able to be brought into service when needed for a few days suggested to Mr Scully that there was “some give" in the system.

“It suggests to me that perhaps Transport for NSW needs to have another look at how it might be able to manage its maintenance cycle to free up eight carriages,” Mr Scully said,.

“Eight carriages isn’t a lot.”

The New Intercity Fleet is scheduled to start rolling out late next year, starting with the Newcastle line.

There is the possibility the old carriages could be moved to the South Coast line when that happens, so Mr Scully said all that was needed now was an interim measure.

“That’s less than 12 months and we’re talking about eight carriages,” he said.

“I wouldn’t have thought that would send the system and the maintenance schedules into meltdown.”

Mr Scully has written to Mr Constance asking him to commit to reallocating carriages from Newcastle to the South Coast when the intercity fleet is introduced.

Transport for NSW has said any redeployment would be considered “closer to the time”.