In this post I'm going to run through some of the options for terminating Pendolino style trains from the South Coast at Central.
The Pendolino series trains (European version) have a car length of 26m (but cab ends don't need to be on the platforms), and come in odd numbered sets. A 7 car trains is 180m long, but only need 130m of platform length, so are comfortably supported by the suburban platforms. A 9 car train is ~230m long, but needs a 180m of platform. 20m longer than a standard Sydney suburban platform. A "top & tailed" train is 14/16/18 cars long, or 364, 416 or 468 metres long, needing platforms 314, 366 or 418 metres long, 25m longer if the cab needs to be on the platform.
So these are the options as I see it, very few of them are mutually exclusive:
Option 1: Platform 26/27 (that old one)
Short (sub 100m) tunnels, then a connection to the Illawarra Main down, and a facing crossover a bit further south somewhere.
This could cross the Airport down on the level (terminal arrivals would oppose Airport Down movements), be built 6-8m lower and "fly under" the airport down, or the Airport Down could be rebuilt as a flyover.
Optionally, the road could be lowered 6m and "fly under" the Airport Down.
Option 2: Platform 21 and/or Platform 23
Extend Platforms 21 and/or 23 to 180m.
Re-install crossovers on the flying junctions with bi-di signalling (UP Illawarra main for platform 21, DOWN Illawarra main for Platform 23)
Crossovers on the Illawarra Main at Cleveland St: trailing for platform 21, facing for Platform 23
Platform 21 departures oppose Sector 2 via Sydenham UP services.
Platform 23 arrivals oppose airport DOWN services.
Option 3: Platform 4 (or 1, and/or 5) at Sydney Terminal.
- Remove the crossovers from the mains to the suburban section & replace with a high speed facing crossover.
- Extend platform 4 (and optionally platform 5) to be 400m long, installing an exit to Regent St, and access to the Devonshire St Tunnel
- Upgrade the points connecting the Illawarra Dive
The downside to this approach is this will oppose current Interurban operations & Horsnby - Strathfield - Central peaks services (destined to become more common).
On the plus side, it supports 400+ trains.
Option 4: Prince Alfred Terminal
A new terminal in the location of the Prince Alfred Sidings
- Airport DOWN is rebuilt as a flyover
The biggest issue with this is how far the southern end of the platform is from many of the interchange locations. It could be nearly a km from there to the passenger's next journey.
Option 4b: Prince Alfred Terminal/Chalmers St Elevated terminal