The North-west Rail Link is to be extended southwards from Chatswood. New tunnels will be bored from Chatswood under the harbour to the CBD. There are to be stations at Crows Nest, North Sydney, Barangaroo, Martin Place, Park St and Central. There is to be only one station between Central and Sydenham which will be in the Waterloo area. The existing railway from Sydenham to Bankstown is to be converted to metro; presumably there will be an interchange at Bankstown station connecting via double-deck trains to Liverpool and Lidcombe. The metro line is to continue to Liverpool on an as-yet-undecided new alignment; presumably the stations from Yagoona onwards will end up with light rail.
The plan has major issues:
Platform gates require the platform edge to be straight or nearly straight to ensure there won't be any gaps between the train and the gate that might let a passenger get stranded between the gates and the trains. Achieving this straightness will require extensive works at certain stations - track and platforms will have to be shifted. Sydenham will be an especially awkward case because land will be taken from an adjoining busy road. Several other stations will need small slices of land from adjoining parks and car parks. If Bankstown station needs one or two more platforms for interchange, considerable land will have to be taken from the park south of the station.
Expect a year's shutdown of the whole Bankstown line during conversion. Other rail services using Sydenham will be disrupted also, as will be road traffic around and over Sydenham station. Locals are realising the problems. Learn more... and still more...
But Sydney Metro doesn't work like that. The north-west line is being built with quite different technology to the existing network. And the second stage, from Chatswood to Sydenham, is to be built without stub tunnels at North Sydney and Waterloo which were planned in the EIS. The stubs were deleted in the Preferred Infrastructure Report released in October 2016.
Although at least one other line has been mooted and is apparently under investigation, nothing has been said about how it will connect to the City & Southwest line. Will there be an interchange station? If so, there certainly won't be cross-platform interchange. Announcements made so far suggest that the metro to Parramatta is being planned for developers not passengers.
Otherwise, Sydney Metro is a 65 kilometre suburban railway.
In this case, we have been told that a metro railway can carry up to 45000 passengers per line per hour whereas double-deck systems like the existing Sydney lines can barely carry 25000 passengers. Implicitly, conversion to metro will solve all the problems of the Bankstown line. Meanwhile, the NSW Department of Planning & Environment has announced a project called Sydenham to Bankstown Urban Renewal Corridor which seeks to double the population of the same Bankstown line. You can read about this project here; note that submissions closed on 31 January 2016.
It is extraordinary that Sydney Metro is to have only one station between Central and Sydenham and similarly only one station between Chatswood and North Sydney. Many inner areas of Sydney are badly-served by buses due to heavy traffic and are remote from rail stations yet do not feature in metro announcements:
… and slightly further out:
… further still:
Adding stations to an underground railway once it is operating is generally not practicable.
Note that opening the NWRL part of Sydney Metro in 2019 will worsen services to upper Northern Line rail stations and therefore satellite districts of those stations will be even worse off than now:
These areas are apparently to be served by the East Hills line. Residents there fear their rail services will be worse than now but in any case the East Hills line can hardly spare any trains because developments around Wolli Creek and Mascot stations will heavily load East Hills trains.
For an interesting discussion of the project, showing why the NSW government is not keen on building new underground rail stations [yes, the cost!] see this SMH article.
The metro announced so far will not fully utilise the expensive sub-harbour tunnel. If the claimed capacity of 45000 passengers per hour each way is to be used, the metro will need to service more areas north of the harbour and perhaps also some more areas south of the harbour. There was to be a Hurstville line, taking over the Illawarra Local tracks south of Sydenham, but the Sydney Morning Herald reported on 3 February 2016 that the Hurstville idea had been dropped.
It is perplexing that the Western Metro, a line running from the CBD through perhaps Rozelle or Balmain westwards to Parramatta or beyond, is being touted by the current NSW government. The Rees government started a similar line in 2008 and it progressed to the stage of acquiring property in Pyrmont and Rozelle but was cancelled by the Keneally government. The mistake was lampooned by the Liberals. But some of the same management and planning staff are involved now as then.
Learn more about Sydney Metro and see a table showing average station spacing on many overseas metro systems. Average station spacing is easy to calculate and is a useful guide to average trip length.
Also see this EcoTransit video about the project.