The state's new intercity trains have been labelled a "lemon" by the Rail, Tram and Bus Union despite an independent review declaring the $2 billion fleet "safe".
The RTBU's criticism of the South Korean-made trains, which were due to begin running between Newcastle and Sydney this year but only started arriving last week, came in response to release of an "expert safety review".
The NSW government commissioned the review after union concerns about how the trains will operate.
Drivers will become responsible for operating train doors on arrival and departure from stations, and for carrying out a safety check process.
Cameras will be used to monitor the train and platform, rather than a guard watching from an open door at the rear of a train.
The trains can actually operate without a guard, which the union has previously criticised, but the NSW government maintains their positions will not be disposed of, rather changed to a customer-service oriented role.
The review found the operating model was "safer than comparable rail operations around the world" and the procedures "applied internationally for many years with acceptable levels of safety".
However, those conclusions were "dependent on an acceptable image quality being displayed on the CCTV monitors" for the driver and guard to view, and the CCTV and door safety systems functioning "as specified".
The review made multiple recommendations to improve the model, including revised training.
But RTBU NSW secretary Alex Claassens said the trains had a "design flaw" that left guards unable to "properly monitor commuters in the crucial moments before the train leaves the platform".
"The NSW government knows it has bought a lemon in the New InterCity Fleet and it's doing everything it can to try and cover up this glaring mistake," he said.
"We've got grave concerns about the independence of this report, which is why the union is commissioning its own review. The train guards, drivers and station staff know that these trains aren't safe."
The first two of 55 new trains arrived via Port Kembla last week. The fleet will replace the decades-old V-sets.