Belly,
There was a serious part to my post as well.

What do they do in far larger cities than Sydney?

Glad I live rural, no traffic much but increasing. I past 8 vehicles on way to town last week. That is a record. Do not know why Sydney radios have traffic reports, I can't see any problems.

Comon, other places work around it, don't they?

StGeo & others,
Tunneling underground would be virtually impossible in
the CBD now with all the water, electricity, communications tunnels
sewage and railways that are there now that run every which way down there.

When I said interstate transport being banned, I am visualising that
rationing would be in place and not sufficient fuel would be allowed
for such journeys. There would be a big reduction in car traffic also.

As it is now, there is talk of either banning cars in the CBD or having
a zone system like in London with a zone charge.

All these things are what we pay politicians to plan for but they
simply do not do the job for which they are paid.