A few come to mind – this 1960s one on the goods lines at Sunshine North:

https://railgallery.wongm.com/melbourne-stations/F117_2467.jpg.html

This one on the Dandenong line near Noble Park Secondary College:

https://railgallery.wongm.com/melbourne-stations/F113_9978.jpg.html

Furner Avenue in North Geelong under the goods lines.

https://www.railgeelong.com/gallery/geelong-ballarat/furner-avenue/E120_9531.jpg.html

Is there any example of only a pedestrian underpass being constructed anywhere in Victoria, and not as part of other construction like a station?

Yes, that could be much easier. It appears suitable. Hopefully, there’ll be many similar crossings along there. However, would the new main sewerage pipe parallel to the tracks prevent it? That pipe and reservation are mentioned throughout the Donnybrook report as major restrictions on possible designs of the new station.

One can find a copy of the standards here:

https://slidex.tips/download/vriogs-railway-station-design-standard-and-guidelines

It’s funny when they ignore those guidelines whenever they are too hard to meet – just look at the pedestrian subway at Southland station, opened in 2017.

I’d assume the only way to lower the tracks through the tunnel would be to dig up the road above for the second time!

http://wiki.prov.vic.gov.au/index.php/VPRS_12800_P7_C_0481

As for remarshalling double stack freight trains, in Adelaide trains headed to/from Melbourne have their second level of containers added/remove for the trip west to Perth.

That would have to be the longest ramp in Melbourne, given the fact that it doesn’t turn back on itself anywhere.

Excavating either side of the tracks to provide a wide Tarneit-style pedestrian underpass would be an easier option:

Elevating or lowering the railway would be far more painful, given that the main Melbourne-Sydney line runs through there.

I should really finish off my blog post on said topic on day…