The roads people got it easy - they were able to do it with a bridge, something that won't really work with rail.

A bridge won't really work with rail????

Do you have engineering qualifications?
Or can you provide a web link to support this claim?

I think you statement claiming a rail bridge can't be done is simply garbage, until proven otherwise.

A sea bridge could be built for the railway. Of course it would cost huge amount of dollars, but I would think a 15km sea bridge / sky rail is cheaper than a 15km tunnel.
The sea bridge would start just south of the clifton tunnel / sea cliff road bridge. It would go past Stanwell Park Beach and go back over land near Bulgo Beach / Otford Lookout. The bridge would then have to continue to just south of Waterfall station. I measured it at approx 15km long. The bridge would save about 15-20 minutes travel time.

Some people will try and say a rail bridge over the sea can't be done. If there is evidence the geology of the seabed is unstable, then yes I agree it's not possible. If its possible to build Hong Kong-Zhuhai bridge then it is possible to build this bridge as well.

It would be a visual eyesore marring a beautiful coastline. Not on.

Would be fun to ride during an East coast low.

It's certainly not impossible, but I think there are a coupe of issues. One is that part of its potential footprint is occupied by the Seacliff bridge. A pity they couldn't have thought ahead and designed a road-rail bridge. The other issue is that, whereas that Hong Kong bridge seems to be in a fairly placid marine environment, the south coast gets smashed by the Tasman Sea which, in full force, is very powerful, leading to potential damage and service interruption. Either way, it's all subject to geological studies.

It seems to me that the drift of things here is the the Waterfall-Thirroul section of the line will be a difficult one to solve. There will doubtless be a solution but it will be expensive and government has so far shied away from tackling it. The best path for discussion in the shorter term is to look at performance along the potentially fast sections of the line (which actually constitute about 80% of its length) between Sydney and Waterfall and between Thirroul and Bomaderry. These sections, which contain nothing serious in curvature or gradient that would inhibit the performance of electric trains, are presently run waaaay too slowly. How to fix that?

We are not talking new stations which are obviously built in high density areas with all the bells and whistles, we are talking about the issues of upgrading older stations with very small patronage, say less than 100 per day and avoiding DAA compliance where economically it simply doesn't stack up.

Yeah we are talking about new stations. That was the whole original point bought up by someone on this topic as to why we don't have more new stations. Older stations obviously have grandfather clauses but anything that is done to them in regards to upgrades must be DDA compliant. Whether that means lifts or fixing the ramp grade.

Anyway back to topic I think duplicating to shellharbour should solve many issues south of Wollongong where trains are waiting for other trains on the current single track sections for much longer then they should be increasing travel times.

Reducing the travel time further will require a new twin tunnel to be built. Using the old tunnels is just a silly idea as they are single tunnels for a start and nowhere near meeting the needs for a modern rail system. They also way to steep and a longer tunnel to Thirroul will help with reduced travel time for passenger and freight.

Lifts would still add a significant cost compared to a station without no lifts, a station with no lifts has no moving parts, and only needs electricity to run the lights, opal readers, and PA system.

Lets look at the most recent lines built, where stations are (in bold) and where they should also be (in norma