SRT "super-station" at Martin Place/St James is best use of existing high "sunk cost" infrastructure

My last post described the "super-station" concept where a station on one rail line can join up two previously separate stations of other train lines, so as to form a "super station" that allows interchange across three separate lines (eg. London's Crossrail at Liverpool St/Moorgate).  These super-stations are also quite viable construction-wise, as they leverage existing surface access, thus minimising expensive surface excavation of large station boxes.  As seen in the Crossrail station diagram below, most of the Cross rail super-station is formed by TBM bored tunnels, and needs only relatively small open cut concourses, that extend/use existing station facilities:



The Pitt St/Town Hall super-station in my last post is an idea for a future (post SRT) stage, but what about other more immediate opportunities during SRT construction itself?  After some further thought, Martin Place/St James strikes me as the more immediate super-station opportunity.  As seen in the map below, these two stations are only 250m apart, so just the right distance to link up with an SRT station running underneath:


Importantly, enabling interchange at Martin Place/St James is exactly the right way to balance patronage and passenger crowds across the CBD station network.   As seen in this table from the 2012 NSW Infrastructure strategy, St James & Martin Place are relatively under-utilised CBD stations whereas Town Hall is quite overloaded:

CBD Platforms and Station Entries during PM Peak (15:00 – 18:30):

Town Hall	6	39,000
Wynyard	4	33,000
Martin Place	2	12,000
Circular Quay	2	8,000
St James	2	4,000
Museum	2	6,000
Total	18	102,000

The high patronage of the latter reflects the convergence of Eastern Suburbs and West suburban/local lines (a total of 3 track pairs), whereas the poor patronage of St James reflects it only servicing one track pair.  It makes a lot of sense then to provide an integrated Martin Place-St James SRT super-station, that can offer interchange between the Eastern Suburbs, East Hills and SRT lines, rather than three separate stations that only allow access to one line each.

The result will be a very nice balance of interchange patronage at three major CBD "super-stations":
1.  Southern interchange points at Redfern/Central stations, eg. passengers coming from the south can get off at Redfern or Central, and interchange early rather than crowding into the more constrained inner CBD stations.
2.  Western interchange point at Town Hall, eg. North Shore line passengers can transfer onto Eastern Suburbs or city circle local lines and where interchage with SE & CBD light rail can be done.
3.  Northeastern interchange point at Martin Place/St James, eg. SRT line passengers coming from the north can get off earlier and interchange onto Eastern suburbs & city circle trains as they leave the CBD (and have already unloaded their passengers) - rather than causing crowding at Town Hall or at Central.

This "triangle" of CBD superstations would thus better utilise existing latent station facilities and passenger capacity, and ensure existing, high "sunk cost" infrastructure is used to the fullest and most cost-effective extent.