Possibly 2, or more consortia get pieces to do.
In the meantime a hub at Sunshine has linked Geelong/Ballarat/Bendigo/Seymour(and their preceding Metro) with the airport and each other, plus of course the rest of Melbourne to the South and East via MM1.
That hub, with a 5-10 year head start, will have established travel patterns for pax to work their best way around.
Building a short-cut from Carolyn Springs via Watergardens to the airport would be of questionable value. A business case for it's owm merit.
Im very much aware it's not an East V West issue. I think they call it a play on words.
Melbourne Airport has already confirmed they will build an underground station.
If MARL and SRL are built by two different consotriums I can't see the TBM for one consortium helping out the other. They will most likely be two seperate projects, years apart.
As for Sunshine, the idea of having 'minor' interchanges further down the branch line (Sunbury & Melton) is to spread peak passenger loadings. You are going to have 8 different lines interchange at one station. This is a lot of people all in the one location, even with an upgrade Sunshine still needs to handle tens of thousands of passengers during the peak hours.
Station locations are just suggestions and when and if the North West Section gets built I imagine the government off the day will have a business case to confirm the best locations for said stations. Watgerardens and Caroline Spring are the closest the outer north west has to activity hubs. SRL will allow for more intense development of housing and Jobs around the stations locations, as is planned in the east. The lack of any major education or jobs anchor in the north west is a prime example of the differences best East and West.
In the East SRL is intended to serve those exisiting hubs that already have strong demand. In the North and the West SRL will be catalyst for these hubs.
For a 2km tunnel at the Airport, could not cost justify a TBM on its own.
Either use road headers at double the unit cost(and price yourself out of the bid), or sell a used machine to another piece of the puzzle.
It's not helping each other, it's good business.
Would be interesting to see who bids to do the lot.
It's also not years apart. Both MARL and SRL-east are slated to start 2022.
If SRL-west starts after MARL is finished, that's still 2025 at best, with another 5 years to meet SRL-east. I doubt the Airport could counteance 2 separate work sites setting up, doubling the inevitable disruption.
I would hardly call Sunshine an 8 line junction. There is one extra service, and unlikely to need a new platform. Current Up/Down for RRL and Sunbury remain the same, with perhaps Bendigo trains actually stopping.
When Melton and/or Wyndham Vale are sparked, that is another pair for the station to manage. That's regardless of SRL or MARL and one of the more expensive problems for that project.
Last time I worked at Vic Uni, it was a major centre. 15 years on, its doubled. More students than LaTrobe.
Tullamarine is the light industry centre.
The extra stations you hypothesized are middle of ever growing dormitory suburbs.
Nothing on the horizon for jobs, except huge plans for Arden, which is probably not west enough for your purpose.
There is no public state date for MARL, we are yet to even see what it will be. SRL Stage 1 has an expected start date of 2022, that would be Cheltenham to Box Hill. The Broadmeadows - Airport connection is stage 3, as yet to even have a plan. IF and a very big IF, planing works were to start on stages 2 & 3 while stage 1 is under construction this would allow construction to start late 2020's. The IF is politics, Stage 1 might be all we see depending on the next election.
By the time MARL & SRL roll into Sunshine it will service Melton, WV, Sunbury Metro Lines; Ballarat, Geelong, Bendigo Interurban Lines; Airport & SRL. That is a lot of pax interchanging in the one location.
As I've said SRL does not need to serve the same purpose west of the city as it does east of the city. The Eastern suburbs already enjoy far superior public transport, with a collection of lines already at TAG frequency, tram links and a dense bus network. The outer reaches of the east are suffering from the same problem at the west. However, the vast majority have good links to public transport.
This is not the case in the west. There are only two metro lines running at capacity during peak, no far reaching tram network and an add hoc bus network that does not offer the same suburb to suburb connections as the east.
SRL may be the 'last mile' connection in the east and north, connecting pax from branch lines to employment centres. In the west it will need to do a lot more heavy lifting and will be the principle public transport link for many people. All lines to Sunshine looks good on a map for politicians as no detailed planing for this stage is likely to take place during their time in office. Watergardens, Caroline Springs are already minor employment clusters with the potential for major development to serve as hubs for the hundreds of thousands that live around them. Connecting these minor hubs into major clusters such as Broadmeadows, Doncaster and Box Hill serves the SRL's primary objective of creating 20 minute cities as outlined in Plan Melbourne.
A lot is going to change before SRL gets anywhere near the west, a business case will be conducted just as one is now in the east to make sure the project gets maximum bang for its buck. Regardless of where stations may or may not sprout up, I highly doubt all lines will lead to Sunshine for the completed project.