I cannot find an old Mt Barker train timetable so a few comparisons
So from this I'm guessing a Adelaide station, Goodwood station, Belair station then all to Mt Barker Station service would take 75 - 90min, which is not too bad …
You're looking at the outer end of that 75-90 minutes.
Attacking the approximation of the time from another direction:
ARTC Master Train Plan time (yes, the usual disclaimers about the MTP apply) for the Overland going non-stop from the passing loop at Mount Barker Junction to Keswick: 62 minutes.
Mount Barker to Mount Barker Junction: 5.2km of tight curves which would keep speeds down to ~45 km/h, probably about 8 minutes.
Keswick to Adelaide: 7-10 minutes, depending on how things go with junctions, network interfaces etc
Time lost at intermediate stops (Adelaide Showground, Belair, Mount Lofty, Bridgewater, Balhannah): 8-10 minutesTotal time: 85-90 minutes
Getting a train to 'Adelaide' in the 21st century and getting dropped off on the wrong side of North Terrace in borrowed parklands: priceless
So from this I'm guessing a Adelaide station, Goodwood station, Belair station then all to Mt Barker Station service would take 75 - 90min, which is not too bad and if the Belair line is popular, then maybe this would work if a few services a day.
- Morning peak direction,
- Midday up and back
- PM peak direction
Sat/Sun, return to City in AM and PM
1 x SG set with spare would do this easily.
Decent service pattern proposal, but thought would need to be given to how the reliability of the service would be maintained against ARTC's regular pattern of doing off-peak track maintenance somewhere along the route.
Running a micro-fleet of SG cars would also hit service reliability.
The hard part is the last 1.5km of DG trackage from the Y junction near Adelaide station through a number of points. Would it be worth it?
Not worth it for just a couple of trains a day. Initially terminating at Adelaide Showground might be the best available option to get an initial trial service up and running.
But it does present a good case for the gains to be made at a fraction of the cost by improving conditions for buses travelling along Glen Osmond Road. A 55 minute peak service (50 minute off-peak) should be the target, and you would get improvements for the local buses on Glen Osmond Road bundled in for good measure.
Each station currently out of service needs the full 21st century DAA package upgrade, plus likely 2 tracks being converted to DG into Adelaide station, that won't be done for less than a few million.
New SG platform at Adelaide Showground (easier than upgrading Goodwood, better connections) if ARTC allows it
Upgrade at Belair – or at Blackwood instead for a more useful stop
Upgrade at Mount Lofty
New stations at Bridgewater and Balhannah if ARTC allow them
Upgrade or new platform at Mount Barker
If heritage listings cannot be retracted, expect the old station upgrades to go well past a million dollars each.
Dual gauge into Adelaide, including link line at Mile End and signalling installations.
Rebuilt track from Mount Barker to Mount Barker Junction, including signalling installations, secure stabling facility, connection to ARTC network.
Stabling/maintenance facility at the Adelaide end.
Also, can suitable slots be made available by ARTC?
The Adelaide-Melbourne line is pretty sleepy these days, only 4-5 trains each way per day.
If the operator is willing to pay, they'll get the access. The tougher question is whether ARTC will allow all these new passenger stations on their network - unlike the Vic and NSW lines which they lease (with conditions) from the respective state governments, ARTC actually own this route and would have a far greater say.
Rail to Mt Barker would be possible if done in conjunction with a tunnel upgrade of the interstate line with a tunnel from near Mitcham to Callington. This tunnel could be fairly straight, have four tracks down to under Mt Barker (two for each gauge) and also a further station under Mt Lofty. The grade would be approximately level with Callington being slightly (three metres) lower than Lynton. However this would require heaps of finance and political will.