There was also a 1990s study by SMEC that was considered to have overlooked the issue of the mine workings, something that would also be a factor in the way of that internal study. The Coalcliff colliery workings extend many km inland, well past the freeway. Unless there's been some new technology that I don't know about, there's a basic reluctance (refusal) to build tunnels that pass over mine workings where the latter are partly unknown (not properly mapped) and can't be dealt with. There's basically little alternative but to stick to the coast and that's where the unstable scree slopes are. The Connell Wagner study iirc did manage to address all of those issues and come up with what looks like a workable alignment. I recall that it also enabled station stops at some of the towns, so it's not that there was going to be no stops between Waterfall and Thirroul.

Tony P

---InTramsDownUnder@..., <gol80579@...> wrote :

There was an internal proposal for a tunnel from Thirroul to the top of the escarpment and then a line to roughly follow the freeway to Waterfall which was mooted in the early Nineteen Nineties. As it was internal it didn’t get very far. A now deceased member of SPER was involved. As has already been stated electric traction would be required as diesels would not be an option. No doubt a vote, er, sorry passenger count would have been done on the stations which would have lost their service withe closing of the old line. Helensburgh was to get a new station near the freeway, it’s third.
Geoff O.