Edited 09 Jan 2020 19:57, last year, edited by BDA

The short south from my memory has ruleing grades off 1:66 on the down (Exeter Bank) and 1:66 on the up (Wingello Bank).
Personally I wouldn't bother with most the original alignments on the southern line north or south of Junee .

In the past I got to drive the southern line as far as Junee and had plenty of road trips in between on the Hume Hwy.
Had plenty of road trips over grades on the Hwy such as the one at the south end of Bredalbin Plains , to run trains over a similar alignment and grade is worth the pain to go sailing over the top of the range and on past Gunning . Imagine not having to snake down the range into places like Fish River and Gunning , imagine a line speed for loco hauled of 115 virtually everywhere .
That "Main Southern Line " is dark ages crap virtually everywhere . You must remember even going up the southern highlands to Mittagong on the Hume . Yes there are several very tall and expensive concrete bridges over significant gorges  , it's the lack of things like these that chain rail alignments to the garbage they are today - by todays standards .
Aside from Catherin Hill I can't think of one significant grade on the "down Hume" in this area that would be an issue for pass and freight trains with adequate power .
Spaniards isn't so bad on the road and doesn't force you through Mauldon bends or the "balloon loop after Picton .
I could go on but you get the point .
I believe the goal for rail freight in the future is to get there sooner and to offer an attractive price .
Blind Freddy knows the only reason road can do this is because its infrastructure is so so much better than rails .
Its been said many times before , and by me as well , imagine how poor road freight performance would be if it had to run over the Hume as it was in 1970 . AFAIK there has been little or no improvements alignment wise to the main southern line since something like 1932 ? And this is the exact reason why rail fails dismally compared to road .
And to the XPT experience , I have never worked on them but had plenty of cab rides down there , in a few various seats …
From what I'm told they didn't make serious inroads into running times compared to the loco hauled expresses . It would have been remarkably obvious to the people operating them that the section times weren't often that much better . It's not rocket science . Put higher performance trains on a twisty windy track and expect good running times ? Lunacy .
The X may have increased Nev's electile capacity , and cost the state of NSW a bomb , but it was still way cheaper than paying for major rail realignments .