Cycling in Sydney Australia
The S-Bahnen und U-Bahnen are a bit like that in Germany- often stacked vertically.
Electric train tracks can be covered over without an exhaust problem with ease- by comparison with roads needing pollution stacks. Lots of parks like that in Paris, with Metro below. Imagine the existing rail line covered over from Parra to CBD, with parks, trams and a f'off cycleway on top?
When you have done that Parra Rd could be one traffic lane and one bus lane only in each direction, with urban amenity people space in the rest of it. No need for M4 east, the peeps without tools and cranes can use train, tram, bus or bike all with a cheeky short journey time.
Having a full capacity surface train network is not much of a drama space wise.
The 6 lines strathfield through to central flow 18000 people an hour each, so in the inbound peak, the 3 inbound tracks, flow the equivalent of 45 free flowing at capacity single occupant motor vehicle lanes - which rarely even occurs in practice. This is also why the inner city railway has so many overbridges, because the railway network can be relatively sparse compared to a motorway network, the cost of crossing it repeatedly is less, so usually they have less of a divisive effect on communities, and the stations tend to be surrounded with shops and the like, where as motorways only really support car accessible only service stations.
Incidently, nearly every street in Sydney is actually a 4 lane road, its just that 2 of the lanes are blocked by private transport devices that are nearly never in use.