WITH around 4.5 million people currently living in the greater Sydney area, and growth in the region anticipated at 30% between now and 2031, Australia's largest city requires a reliable and efficient public transport alternative to cope with a projected population of over 6 million people by 2031.

The North West Rail Link (NWRL) started out as just another heavy rail line linking in with the suburban rail network. But despite a turbulent beginning, once completed in 2019 this stand-alone metro line will be the foundation for a wider rapid transit network and is on track to become a game changer when future urban rail projects are considered in Australia.

The North West Rail Link is a case study on how transport planning in Australia is plagued by partisan politics. It took 15 years to come to fruition and was abandoned and revised several times during that period.

The need for a heavy rail link from Epping to Castle Hill to connect the expanding suburbs of the northwest with the Sydney suburban network was first identified as far back as 1998 with completion envisaged by 2010.

For a decade the proposals faded in and out of public view several times before being revamped in 2008 into a rapid transit 'metro' style system. Unfortunately the global financial crisis and budgetary constraints meant the project was abandoned in favour of a more modest central business district (CBD) metro proposal in a little over six months.

However, the NWRL was back on the agenda two years later when the CBD metro was dropped and the project again took centre stage as the government's preferred big-ticket public transport option.

The Liberal party's victory in the 2011 election led to the final rethink. While the new government initially committed to the original heavy-rail proposal, within a short time a decision was made to once again run with the North West Metro project.

The model chosen for the $A 8.3bn ($US 7.19bn) project uses a mixture of direct government investment and an availability public-private partnership (PPP), though the government has indicated it is likely to come in under budget. In its 2013-14 budget forward estimates the NSW state government allocated $A 3.3bn to the NWRL over the next four years, with $A 360m budgeted in the 2013-14 financial year. The project's total private capital is over $A 1.8bn, including senior debt of $A 1.55bn.

Detailed planning for the rail link was completed by the end of 2012 and tenders for all the major works associated with the NWRL were called in early 2013.

Much of the new 23km line between Rouse Hill and Epping will run in 15km of twin bore tunnels between Bella Vista and Epping, with a 4.4km continuous viaduct, or 'Skytrain' as it is being marketed, between Kellyville and Rouse Hill. The remaining 4km between Bella Vista and Kellyville and Rouse Hill and Cudgegong Road will run at grade.

At Epping the new line will connect with the existing 13km Sydney Trains Epping - Chatswood line which will be converted for rapid-transit operations, establishing Chatswood as the major interchange between the NWRL and the Sydney Trains network. However, there are plans to eliminate the need for interchange and extend the line through to the CBD as part of the broader expansion of the rapid transit network, although no timeframe has yet been set for this subsequent phase.

The NWRL will include a number of firsts such as a dedicated single-deck train fleet - a major departure from the heavy-rail double-deck trains which currently provide all of Sydney's suburban services - metro style frequencies and platform screen doors.

It will also be the first driverless passenger line and the first to be built and operated by the private sector from the outset, albeit under contract to the NSW government.

The works and future operations for the NWRL have been split into three major contracts, all of which have now been awarded with construction getting underway earlier this year.NWRL-Alstom-train1

The $A 340m surface and viaduct civil works contract commenced in June after it was awarded on a design and construct basis to the Salini-Impregilo joint venture in December 2013. The contract covers construction of the elevated Skytrain section as well as other surface works including bridges, embankments, cuttings and earthworks.

The viaduct and a 270m cable-stayed bridge over Windsor Road at Rouse Hill are the most visible elements of the 36km link. The project developers were also keen for contractors to integrate the final designs with the line's surroundings.

In September, the first of four tunnel boring machines began excavating the twin 15km tunnels required between Bella Vista and Epping as part of the entirely government-funded $A 1.15bn tunnelling contract awarded to the Thiess-John Holland-Dragados joint venture.

The 120m-long machine, named 'Elizabeth' was built by French company NFM Technologies at various global locations and then transported to Newcastle, New South Wales, for assembly at the Bella Vista work site.

The tunnels will be bored at an average depth of 27m, and as deep as 63m, in rock that is mainly formed of abrasive sandstone. In early October a second 6.99m-diameter double-shield TBM was being assembled at Bella Vista and was expected to commence digging before the end of the year.

The first two TBMs will excavate 9km twin tunnels between Bella Vista and Cherrybrook, with the other two boring the 6km from Cherrybrook to Epping, each machine gradually building up to a full tunnelling production rate of about 120m per week.

As construction got underway, attention shifted to the operations, trains and systems contract (OTS), which is valued at $A 3.7bn, and is the largest on offer. It includes construction of the line's eight stations, building and operating the stabling and maintenance facility at Tallwaong Road, upgrading and converting the existing 13km railway between Epping and Chatswood for rapid transit operation, along with provision of the automated rolling stock and systems for the line, including 1500V dc electrification, the same as the existing network.

It also encompasses the private element of the project and was officially awarded to the North West Rapid Transit (NWRT) consortium comprising MTR Corporation, John Holland, Leighton Contractors, UGL Rail Services, and Plenary Group in September, after the group was provisionally selected in June.

The consortium is responsible for ongoing operation of the NWRL for a period of 15 years while the government will continue to set fares in line with the rest of the Sydney suburban rail network. The NSW government has not yet released full details of the OTS contract, other than it will be delivered as a PPP, although Plenary Group says it has finalised the private sector financing for the $A 3.7bn deal.

As part of the OTS contract Alstom will supply 22 six-car fully-automated Metropolis trains for the NWRL along with its Urbalis 400 communications-based train control (CBTC) system at cost of €298m. It will be responsible for project management, design, supply, manufacturing, testing and commissioning of the rolling stock and the signalling system.

Alstom says the Metropolis trains have been adapted to Sydney's needs and will feature three sets of double-doors per car for improved passenger access and flow, CCTV, emergency intercoms, and the latest passenger real-time travel information.

Initially the government specified longer trains and five-minute frequencies for the line. However the consortium came back with an alternate plan to run at a slightly higher frequency, but with shorter trains. As a result at least 15 trains an hour will serve the NWRL to Chatsworth at peak times, and with platforms built to accommodate eight-car trains, provision will be made to extend the trains to eight cars if required.

In the longer term Sydney's Rail Future plan commits to a second underground rail crossing under Sydney Harbour which will allow direct trains to operate from the NWRL to the Sydney CBD and beyond via Chatswood.

Sydney Rapid Transit (SRT) would extend the rapid transit concept by 30km from Chatswood through to the CBD with the creation of additional tracks for 3km leaving Chatswood combined with new 12.5km twin tunnels and conversion of existing track to Sydenham, Bankstown, Cabramatta, Lidcombe and Hurstville in the western suburbs.

With capacity to run up to 30 trains per hour in each direction through the CBD there would be three new underground SRT stations at Central, Pitt Street, and Martin Place to ease chronic congestion at existing stations such as Wynyard and Town Hall.

If it proceeds, SRT would free up a substantial number of paths on the existing network and provide capacity for an additional 60,000 passengers through the CBD in peak periods.

The state government is yet to announce cost estimates for the SRT extension and has indicated it may not proceed unless it receives a mandate at the March 2015 election to sell off government owned assets to pay for the project.

If the experience of the NWRL is anything to go by, there are almost certainly some political twists to come in this tale. But with tunnelling on the NWRL link well underway by next year, 17 years after the project was initially conceived, it may provide sufficient encouragement to convince the next government to push ahead with the next phase of the project to meet the needs of an expanding population.