An artist's impression of the new trains that will be built in South Korea. That is too narrow for the Korean-built trains the government ordered last year, which will be about 3.1 metres wide. The work proposed to bring the line up to standard will involve replacing or repositioning tracks along parts of the 75-kilometre rail corridor, extending platforms at Katoomba and Lithgow stations, and adjusting the overhead wiring and signalling systems. The platforms at Katoomba and Lithgow will need to be lengthened because services terminate at those stations. The report by Transport for NSW says all doors on the new trains – which will be up to 205m long – will need to be able to be opened at those stations to allow passengers to get off. While much of the minor work can be done during ordinary hours, a large portion of the project will have to take place during 10 scheduled track possession periods over two years. They typically involve shutdown periods of 48 hours over a weekend.

Blue Mountains Line project. Credit:Transport for NSW However, the report says that five of those possession periods for the line between Newnes Junction and Lithgow will have to each last for as long as 12 days. Transport for NSW will also seek separate approval for improvements to a section of the line that passes through what is known as the "10 tunnels deviation" in the Blue Mountains. Labor transport spokeswoman Jodi McKay said the amount of work needed to make the line capable of handling the new trains was astonishing. "Not only will a staggering 60km of track need to be ripped up – but now we discover that overhead wiring, signals, station platforms and even canopies will all need to be altered," she said.

"Not only that but all the extra work needed – that the government didn't foresee – will mean commuters on the Blue Mountains Line will have to contend with two years of rail closures before they get a glimpse of these trains." But Transport Minister Andrew Constance accused Labor of a "scare campaign with absolutely no substance to it", saying the government wanted to give people in the Blue Mountains a modern train line that was integrated with the rest of the network. "Currently more than half of all our train fleet cannot service that line and only electric intercity trains [V-Sets] fit the Blue Mountains Line all the way to Lithgow," he said. "Standardising the Blue Mountains Line is a sensible approach and will help to future-proof our network." The government is yet to reveal how much it expects the cost of bringing the Blue Mountains Line up to scratch will be. The $2.3 billion contract awarded to a UGL-led consortium to build the 512 double-deck train carriages does not include modifications to the line or a new maintenance facility at Kangy Angy on the Central Coast.

Loading A spokesman for Transport for NSW said the modification was subject to a tender process and the estimated cost commercial-in-confidence "in order to ensure taxpayers receive the best value for money". The contract for the trains is the biggest in NSW since the government awarded the troubled Waratah project to a Downer EDI-led consortium about a decade ago to build carriages in China. The first of the new intercity trains are due to begin operating services from Sydney's Central Station to Newcastle and the Illawarra in 2019.