Alrighty then, time to throw my hat into this discussion. Because literally my neighbourino is the NSL! So I think I should be listened to because these decisions your making could knock down my house!
It would be very difficult for additional tracks before North Sydney. Say at Turramurra... Where the old Goods Siding was, is now an important Bus Terminal. We got numerous lines that go through there. On the other side, there is a recently built park. And there are plans by the Council to redevelop the town square. Which is currently a big flat piece of concrete. Warrawee has Knox, and has too thin of space to the streets. Wahroonga has a few parks that have Heritage Listing buildings in.
The railway sidings at Milsons Point could be better used as a public walkway, more land for LPS (who I am affiliated with), and Heritage Rail Tours. These sidings could be easily spot just beside Waverton for at least 1 track. There is also room for numerous tracks at St Leonards. This may give even more sidings then there are now. But don't expect more tracks beyond St Leonards. There's just simply not enough space. The rest have been taken up.
This can help seperate the NSL/Northern Lines. And the Western Line. Western Line trains can start at the loosely used Platforms 2 and 3 at North Sydney. We can then close down the Cahill Expressway. Use the former tracks on the Eastern Side of the Bridge. And use the old Platforms 1 and 2 at Wynyard. This is currently a Car Park. Cahill Expressway would become a Predestrian Boulevard. Perfect for Picnics, Cycling, and Festivals above the Railway Corridor! New platforms 3 and 4 would be built at Pitt Street. Just next to the new platforms. New platforms would be built at Central Station. Below the Coach Station. There would be a new station at UOS. Just below Victoria Park. The tunnels would rejoin just before Stanmore. With additional reconfiguring between Stanmore and Strathfield. This would allow the seperation of the MNL, MWL, and OMSL lines.
If I want to go from the Upper North Shore to Central. The trip will go over 40 minutes by the schedule. This is due to unreasonable speed limits on the North Shore Line. Going Northbound from Pymble to Turramurra can get you over 80 km/h. The track was built in 2009. The track Citybound used to be the same speed on the old wooden sleepers. They put in concrete sleepers on 2016. It became just 65 km/h! And this is a straight track for almost 2km! This is way overdue for something to be done. When they do trackwork almost every night and during the weekend! I don't know how this has gotten unoticed! This is also due to you stopping at every single station. While Lindfield services get to go express! I think how it should work is for Berwora and Hornsby services to go all stations to Gordon. Then Chatswood, St Leonards, North Sydney, then all stations into the City. While services starting at Gordon/Lindfield do the all stations services.
Killara Station would have side platforms instead. This would allow top speeds between Gordon and Lindfield. Which is the longest straight path on the line.
There are plans for the conversion of the NSL (To Hornsby) and IWL (To Homebush) into Metro. These lines would merge into 1. This would happen in the early 2030's. Western and Northern line services would terminate at Sydney Terminal. (Link will be available ASAP)
More weekend services are desperately needed on the Upper North Shore due to overcrowding. Having 5-6 trains per hour compared to the current 4 would be perfect for stations like Turramurra and Waitara. Who are bursting at the scenes with recent development.
The Sydney Trains map doesn't accurately depicte how the services work in the NSL. Except during the AM Peak. Western Services otherwise don't tread past Gordon. Richmond Services terminate at Lindfield. And Penrith/Emu Plains services terminate at Gordon. Hornsby and Berwora services come from Hornsby via Strathfield. It used to be that 2tph would come from Berwora, 2 from Hornsby. Which would go to Penrith/Richmond. Emu Plains Services would start at Gordon. Hornsby via Pennant Hills would use the ECRL. What was originally gonna happen is that the line would start at Westmead. Go to Parramatta. Then new tunnels to connect at Camellia. Then use the Carlingford Line. Then use new tunnels to Epping. Use the ECRL. Then quadruplicaton between Chatswood and St Leonards. Then a second Harbour Tunnel into the City. Then proberbly using the Bankstown Line to free the bottleneck.
There is not much that can be done until 2024 sadly. In 2019, they did a ton of trackwork to allow trains every 3 minutes between Waverton and Hornsby. Originally, this was only every 10 minutes. This has caused a massive spike in trains on the line. Which means that the NSL has to carry more of the load for Sector 3. This will cause traffic jams in the meantime. More trains than normal are needed on the NSL for tens of thousands of school students.
People jumping onto the Metro will definitely happen at least in the Off Peak. This is because it can take over 20 minutes between Chatswood and the City on via St Leonards. While it'll only be just over 5 minutes from Chatswood into the City via Crows Nest! Google Maps will just direct them there unless if it's set to minimal transfers. This may be different during the peak, as already it's gotten quite overcrowded on the Metro!
The best opportunity to do works on the NSL will be in the mid to late 2020's. For these reasons. It's not the best time right now. But the future is bright.
Now I hopefully don't get an angry mob saying "Burn Ahead, BURN!", with a Tangara screeching "I was saying Boogoaheadoo." when I get back home.