For the past nine months, designers have been crawling over the stainless steel carriage – some of it made from 3D printing – to fine tune aspects of the interior such as baggage storage, bicycle racks and even the colour of seats.

The first of 512 new carriages will begin replacing the state's four-decade-old V-set trains from late next year on the rail line to the Central Coast and Newcastle.

By mid-2020, the new trains being built in South Korea will begin running on the Blue Mountains line to Mount Victoria, followed by Lithgow about four months later and, after that, on the South Coast line to Wollongong and Kiama.

Among the most noticeable features are toilets accessible for large wheelchairs, smaller steps on the stairs between the two decks that make them easier to climb, power points for mobile devices and tray tables.

And in a break from the past, fixed seats with arm rests have been incorporated into the carriages in a two-by-two formation instead of reversible seats like those on the V-set trains.

Internal Transport for NSW documents released under freedom of information laws have shown that passengers have a “general preference for flip seats”.

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But Transport Minister Andrew Constance believes nay-sayers will be “proven wrong” because the fixed seats allow people to benefit from features such as tray tables and charge points.

“It will be a completely new customer experience – far more comfortable and pleasant – and it's one we have taken very seriously,” he said.

“It's not as if this is a train designed for 10 to 12-hour passenger trips.”

Fixed seats are a common feature on most trains around the world, and more can be incorporated in a carriage than reversible seats, meaning fewer people will have to stand.

Transport for NSW's head of the fleet delivery program, Becky Wood, said she hoped passengers would notice the greater space and a more welcoming environment.

“We get a lot of feedback from our customers that one of the things we need to focus on is the feeling of being secure, as well as feeling comfortable,” she said.

“We have really thought about the technology and making it accessible.”

On the exterior of the trains, digital screens will notify people about aspects such as the location of quiet carriages and which ones are fully occupied.

A two-year upgrade to the Blue Mountains line between Springwood and Lithgow will begin late this year to make it capable of carrying the new trains.

Mr Constance said he would reveal the cost of the upgrade when the final contract was signed.

“We have the ability to do this for the first time in 150 years and we are going to do it. I don't see why the people of Lithgow should be denied access to a modern world-class train,” he said.

The government has put the overall cost of the new trains, the upgrade to the Blue Mountains line and a new maintenance facility at Kangy Angy at $2.8 billion.

The arrival of the new trains will allow 225 V-set carriages to be retired over the next few years.

Sydney Morning Herald