The former rail executives say the metro project will undermine the "robustness and reliability" of the existing double-deck network. Credit:Edwina Pickles Prior to the 2011 state election, then Coalition transport spokeswoman Gladys Berejiklian promised to build the long-awaited north west rail link between Epping and Rouse Hill as an extension of Sydney's regular train system. But in government, Ms Berejiklian opted in 2012 to build the rail line as a stand-alone privately run rail project using single-deck trains. This decision included the radical option of temporarily closing the existing Epping to Chatswood rail line, which had opened only in 2009, to convert it to these "metro" operations. This closure will occur for seven months from late next year. The longer-term plans for the metro system involve extending it from Chatswood and under the central city on a new rail line to Sydenham, where it will require the conversion of a 13-kilometre stretch of the existing Bankstown rail line. But the metro policies pursued under Ms Berejiklian as transport minister and then premier have been controversial with many rail experts, who fear it may not be the best use of scarce resources, and that it may undermine Sydney's existing heavy rail network.

Driverless, single-deck trains will run along the new metro line. "If the government had spent $17 billion on upgrading the existing double-deck system by improving signalling and providing track amplification at critical pinch points, it would have got a better overall result," the analysis by the four former rail chiefs said. The former executives include Ron Christie, the director-general for rail who wrote a landmark report on Sydney's train system in 2001. They said in the analysis that the new metro train line "will do nothing to relieve" a bottleneck at Strathfield in Sydney's west where trains on the Western and Northern lines merge. Nor would it resolve the problem of six tracks between Strathfield and Central Station, and the City Circle, the Eastern Suburbs and North Shore lines via the Harbour Bridge, reaching almost saturation point by 2021, they said. The three other heavyweights behind the assessment are John Brew, a former State Rail chief executive; Bob O'Loughlin, a former State Rail director of rail safety and operations; and Dick Day, a former head of planning and timetables at RailCorp.

The relief valve for the network is gone and will result in the network having no escape route. Their assessment, obtained by Labor under freedom-of-information laws, is part of a submission dated July 2015 by a consortium to NSW's long-term transport master plan. Labor's infrastructure spokesman, Michael Daley, said it painted a stark portrait of a project that was "wasteful, disruptive to communities and is nothing more than a Trojan horse for massive overdevelopment in the Sydenham-to-Bankstown corridor". "This experts' report should serve as a wake-up call to Premier Berejiklian," he said. "At $12.5 billion the Metro Southwest is stadiums on steroids." But Transport Minister Andrew Constance said a business case for the metro project found it to be "economic, viable and transformative for the city".

"The only thing Luke Foley and Labor want to do at the next election is to cancel the state's big infrastructure build," he said. "Every global city has a metro network – and in Sydney this will double rail capacity and give people on that south-west metro accessible stations." In their analysis, the former rail executives said the government could "easily find a voter backlash" to the single-deck metro trains, which will have significantly fewer seats than the double-deck trains and therefore require many passengers to stand. "Metro trains are best suited to highly populated, densely trafficked commuter areas over short journey times, not to long, park and ride journeys as is the North West Line from Rouse Hill," they said. The new line from Sydney's north west to Chatswood is the first stage of the metro project, and is due to be opened in 2019 at a cost of $8.3 billion. The government estimates the second stage will cost up to $12.5 billion and open in 2024.

Sydney's two-stage metro train line is estimated to cost about $20 billion. The former executives also describe proposed improvements to the existing double-deck rail, which was operating on an "antiquated signalled network", as "stop gap and short-term". "One can also only conclude these Band-Aid measures are a waste of scarce public funds because announced proposals do not add value or resolve the long-term network capacity problems," they said. "The government plan's lack of vision severely restricts the ability of the heavy rail system to not only cater for growth but also improved services." But a spokesman for Transport for NSW said the government opted for metro rail as a third tier to Sydney's rail network following extensive national and international investigations.

"Sydney's new metro railway will have a target capacity of about 40,000 customers per hour, similar to other metro systems worldwide. Sydney's current suburban system can reliably carry 24,000 people an hour per line," he said. Loading "The conversion of the Bankstown Line to metro rail is integral to taking the pressure off the rest of Sydney's suburban rail system." Construction of the metro line, combined with signalling and infrastructure upgrades across the existing network, would increase the capacity of train services entering the CBD from about 120 an hour at present to up to 200 by 2024, he said.