Thanks Woodford. Going back to around 2008 when rail traffic forecasts undertaken by ARTC in association with the Department of Transport (and in line with Bureau of Transport Economics), were much more bullish than they are now, it was forecast that by around 2014 to 2016, there case for duplicating the Seymour to Tottenham section of the SG. As part of those forecasts daily train numbers were anticipated to be around 30 - 36 or so per day with passenger trains 12 being V/Line 8 (4 each way) and XPT 4 (same as today) and the rest freight around 18 to 24 = 9 to 12 each way.
The real bottle neck as mentioned here was Somerton through to Simms Street with the section in from Tottenham being particularly problematic which is why despite some pulling back in scope, the NE Project still contained new "holding" capacity at Tottenham, a new loop and bi-directional running from Tottenham to Simms street to allow parallel moves etc combined with resignalling and a host of other track works at Simms Street.
Unfortunately with a reduced budget things like the commissioning of passing lanes between Tottenham and Somerton were deferred etc resulting in a diabolical timetable for the NE V/Line services with additional 15 to 20 minutes for crosses etc.
Ever since the commissioning of that passing lane, no one appears to have any real appetite to totally clean up and revamp the timetables and other working for both passenger trains and freight services, between Somerton and Dynon and Laverton and Dynon to maximize the available capacity that exists there. This has been complicated further with lots of light engine movements, wagon transfers etc all through Tottenham etc as well as using the mainline through Simms street for shunting etc making this a very complicated area.
I mention this because there has been consideration from time to time about actually dual gauging the Upfield Line to divert all SG and BG regional and interstate trains to/from the north-east down that line and this then leaves only The Overland to have to go via Tottenham.
At first glance the first response is always what impact will these extra trains have on the Upfield Line and how do you squeeze this through North Melbourne.
In numbers of trains, the Upfield runs three to four per hour. Regional and interstate train frequencies would for the most part add about another 3 trips each way per hour if you combine Seymour, Shep and the NE standard gauge. That brings the total number of train movements each way per hour at the busiest hour up to 7 to 8 per hour. Sure from the junction of the Upfield Line just prior to North Melbourne through to the junction into Southern Cross is a lot more problematic but not impossible. Whichever you cut you still have achieved 3 very significant things. You've removed ALL north east broad and standard gauge passengers of both the SG via Albion and the BG via Essendon. ALL SG passenger trains are also off the North Melbourne Flyover. The BG trains that ran via Essendon now only occupy a very short segment of Metro track around Nth Melbourne and the real issue is adding a relatively short section of DG through Nth Melbourne.
In the overall there are real benefits to everyone including those sqeezing capacity out of the Metro network, getting passenger trains out of the SG Port and Terminals area, and improving both the transit time and reliability for BG and SG services.
This also facilitates the next round of regional gauge standardization in the Goulburn Valley as the biggest passenger infrastructure issue as part of that project has been largely addressed.