Ticking nine boxes out of ten with the prospect of the tenth being ticked
precluded forever into the future isn't really a solution. The problem
exists in other cities too. I don't know all of the examples in Brisbane
but it seems to me that the potential for Gold Coast trains is greatly
inhibited on the sector from the city to Beenleigh and in Perth, the
long-distance regional expresses are slowed along the Midland and Armadale
lines, the only blessing being that the stopping suburban trains move along
quite fast and there is a semi-expressing split on the Armadale suburban
services to move things along faster.

Terminating regional trains to an interchange on the outskirts only works
satisfactorily if the suburban connection is then quite fast, which you get
in Perth and the one Sydney example, the southern highlands interchange at
Campbelltown to fast trains to Sydney (taking advantage of one of the
quaddings of the four main lines out of Sydney). If the interchange is to a
stopping suburban train, it's a mighty incentive to using your car for
regional trips. Even with expressing on the suburban sector you don't get a
very satisfactory solution. Looking at the southern highlands timetable
below (Sydney's fastest interurban service), you can see that, even though
the trains from Campbelltown only stop at Glenfield and the airport cluster
on the way to Sydney, there is a signifcant time penalty compared with the
two direct trains per weekday.

https://transportnsw.info/documents/timetables/93-SHL-Southern-Highlands-Line-20190428.pdf

The more I get windows into transport planning in Melbourne, the more I see
poor decisions and fragmented actions that are too little too late, but I
don't want to comment too much as a New South Welsh, you guys have to sort
it out for yourselves! We also had two terrible periods of setback in NSW
from 1941 to 1965 and 1995 to 2011 but we're well underway now - and I'm
grateful that we have those track amplifications on the main lines, even
though some of them aren't quite as far as they should be. Building a metro
system alongside will also provide huge extra capacity. My conclusion on
Skyrail - yeah, nah.

Tony P