Seeing as Broadmeadows to Strathmore (or wherever it ends) is one continuous downhill run, how far back towards Jacana will the trench need to start to be within regulations?
Or will it be a case of easing the grade between Glenroy and Oak Park from 1:50 out to e.g 1:80, in return for the grade between Jacana and Glenroy becoming more severe (from 1:80 in to maybe 1:50)?
Oliver's bank on the Up side of Glenroy is 1 in 50. At the level crossing it flattens to 1 in 123 rising, and immediately beyond the platform it resumes rising 1 in 68 round the curve to pretty much Jacana.
If the width of the reserve is sufficient, I reckon they'll move the station in the Up direction.
From memory, I think the required vertical distance is 7 metres - that means the cutting entry will be about 400 metres south of Glenroy Rd (including the required vertical curve). That's more than enough distance to put the new 160 metre Glenroy platform on the level immediately south of Glenroy Rd. This will allow them to transition to a new 1 in 40 rising (the maximum allowed) immediately north of Glenroy Rd.
According to Google maps, it's about 300 metres from the northern end of Glenroy Rd to the Down end of Glenroy station. At 1 in 123, there's currently a rise of 2.5 metres in this distance. At 1 in 40, the new track would rise 7.5 metres in this distance. Given a vertical curve, you'd still be in a, say, a 3 metre cutting at the Down end of the current platform.
If you kept climbing at 1 in 40, you'd need a further cutting of around 290 metres to meet the original formation (which is rising at 1 in 68). If I've done my sums correctly. That'd put the end of cutting around 120 metres north of the substation.
If you keep the station on the north side of Glenroy Rd, I reckon the cutting would run out quite close to Jacana.
If you want 1 in 50 instead of 1 in 40 (to match the bank south of Glenroy), you'd require about 570 metres on the 1 in 68 if the station was south of Glenroy Rd. That's pretty well all the way round the curve to not quite where the houses stop on the west side of the line. If the station was on the north of Glenroy Rd, the cutting would be about 1500 metres long. That's pretty well where the standard gauge flyover is on the Down side of Jacana - I wouldn't think that's financially feasible.