The NSW transport minister says the state's new intercity train fleet will be operational within weeks, but the railway workers' union says that's an "April Fools' Day joke".

Andrew Constance on Thursday took a test ride on the South Korean-built trains, which are awaiting approval from the federal safety regulator.

The 55 new trains will replace the intercity "V-set" trains, which are now 40 years old, and will operate on the Central Coast and Newcastle, Blue Mountains and South Coast lines.

Mr Constance said the trains - which were initially expected to be operational by mid-2019 - would be taking passengers within "a few weeks".

But the NSW Rail, Tram and Bus Union has repeatedly criticised a new system that would oblige train drivers to look at CCTV to watch for hazards on platforms, instead of relying on guards to do it for them.

The union says this compromises on train driver and passenger safety, and in November called off a strike over the issue at the last minute.

The RTBU said Mr Constance's claim the intercity trains would be operational within weeks was an "April Fools' Day joke".

"The NSW premier and transport minister are well aware that no rollout of the new intercity fleet is possible until all of the safety concerns are resolved with the rail workforce, as determined by the Fair Work Commission," RTBU NSW secretary Alex Claassens said.

"Having committed to maintaining guards on all trains, NSW Transport Minister Andrew Constance is now appearing to push through changes that will compromise public safety."

Mr Constance insisted the new trains would be the safest on the NSW network and none of the impacted train guards would be made redundant.

He said he expected an agreement to be reached with the RTBU imminently.

"The technology on board has been changing roles and that's where the union has had an issue," Mr Constance told reporters.

"We're not going to see people swinging outside of the trains like we did previously and I make no apologies for that."

Opposition Leader Jodi McKay said the trains "are now two years late and half a billion dollars over budget".