The MATS Plan's route for a King William Street subway (previously posted by another contributor) is no longer available because the foundations of the Festival Centre, ASER and the Convention Centre blocked it. Fortunately this route would give much better access to the City for rail passengers and would serve areas that the trams do not- but it too is under threat if we do nothing.
Though the cost of this would be high, the benefits would be enormous. There is a good reason why all the Australian cities bigger than Adelaide already have railways under their CBDs. It is well known that rail's market share is much higher to places it serves directly, so this would be very effective in reducing the number of cars on the streets and the need for parking.
Stations should be 300m long to cater for future demand, and double ended to serve as large an area as possible (so the station at North Terrace would directly serve City West as well as near the current station). Gawler Place station should have multiple exits on both sides. Central Market station would directly serve Victoria Square and Chinatown as well as bringing many more customers to the market, and the City SW station would encourage redevelopment of the most neglected part of the City. The railway would then join the Noarlunga Line at Keswick, with provision to extend the tunnel to Woodlands Park to avoid capacity constraints and level crossings.
However, URGENT ACTION IS REQUIRED! The route between Gawler Place and Central Market is under threat from two planned skyscrapers at 10 Flinders Street and 51 Pirie Street. This isn’t necessarily a bad thing – it could be regarded as a great opportunity, as incorporating railway tunnels into the sub basements of those buildings could greatly reduce the cost of constructing that section of line. But if the opportunity is not taken, the tunnel would have to be on a far more expensive alignment – either longer, much deeper, or requiring more building demolition.
This is the biggest opportunity we will ever get to transform Adelaide – we must not waste it!