Sydney Metro: extension to Liverpool will untangle Western line

In December 2015, TfNSW confirmed it was considering an extension of Sydney Metro to Liverpool via a direct route that would pass through the vicinity of Bankstown airport.  This announcement also marks the first (major) departure of Sydney Metro plans from the 2012 Transport Masterplan.  However, most people would consider the Parramatta to CBD corridor to be higher in priority, so why is so much being poured into the Bankstown & Liverpool corridors and not the Parramatta/Western line corridor?

As it turns out, the Liverpool extension would not only speed up Liverpool to CBD journeys, but it can also untangle the Western line and create a 200% capacity increment, which should be enough for a Sydney of 10+ million people.  Plus it would also provide a Cumberland line "on steroids", that would have trains running every 2 minutes instead of the current every 15-30 minutes.  The diagram below shows an example of how the Western line "untangling" would work:



More detailed explanation of the above diagram:
(a) Current rail configuration is shown in the left above, potential future configuration is shown in the right above.
(b) GREEN line & stations: Currently trains from Liverpool travel up to Granville, then continuing parallel to the Western line into the CBD's City Circle (stopping at various stops including Lidcombe, Homebush, Strathfield, Burwood, Ashfield & Newtown along the way)
(c) ORANGE line (on right hand side ie: future configuration): If Sydney Metro is extended from Bankstown to Liverpool, then the stations between Merrylands and Liverpool can all be potentially serviced by Sydney Metro - ie: instead of travelling north to Granville, trains travel south and then west to Bankstown.  This route is actually faster for majority of passengers (boarding south of Fairfield) than the current Green route.
(d) YELLOW & PURPLE lines (on right hand side ie: future configuration): Penrith and Parramatta trains now has dedicated use of all 4 tracks passing through Granville, whereas currently they are more or less restricted to only two tracks.  This allows a doubling of train services on the Western line.  Trains using the PURPLE tracks will terminate at Central, whereas trains using the YELLOW tracks continue into the City Circle.
(e) RED line (on right hand side ie: future configuration): Trains from Northern line (ie: Pennant Hills/Epping/West Ryde/Rhodes/etc) have full use of the middle tracks and continue into the CBD joining up with the North Shore line.  Homebush, Croydon, Burwood and Ashfield are exclusively serviced by the RED line (this is so that YELLOW line trains can be made faster, by bypassing all these stations).

What's interesting is that the Liverpool extension is relatively cheap.  At just 8km and at most just a couple of new stations, it is likely a fraction of the cost of a new rail line to Parramatta, which would require at least 22km of new tunnel and up to 11 stations (in the 2009 West Metro proposal).  It also spreads the benefits between both Liverpool and Parramatta more evenly - rather than concentrating most of the benefit on Parramatta, which already has much faster CBD travel times than Liverpool (27 mins vs 52 mins).  The main disadvantage is that it doesn't have the Olympic Corridor land value capture & urban renewal that a Parramatta metro would provide.  (However, Bankstown airport could become an urban renewal precinct with a Liverpool metro passing through it).

Nonetheless, there is a case for both.  Liverpool extension is a "cheap" first step, along with light rail in the Olympic corridor delivering the initial urban renewal goals.  Then a new rail line from Parramatta to White Bay to further augment urban renewal and land value capture at Silverwater and at Flemington.  In this instance, the Parramatta metro is justified and financed by land value capture of new rail catchements, as capacity wouldn't be needed for existing Western line catchments any time before 2050.  For this reason, the light and heavy rail catchments should be chosen to be complementary so as to maximise land value capture and to provide continuous rail catchments and urban renewal from existing Auburn and Homebush town centres all the way out to the river frontages of the Olympic Corridor.   Interchange centres would then be Parramatta and Strathfield.  (Olympic Park itself is a poor interchange point given the increasingly residential nature of development there and the lack of connectivity of it's existing rail station.  However, a "Pippita station" could be located on both the existing Olympic Park-Lidcombe shuttle shuttle line, as well as on the Parramatta metro line):


(For full resolution version of map below, click here)

More info: Sydney Metro discussion paper