All true; and in all reality - you mention London - the ONLY way is underground. With every street on the surface having a finite width, we can reorganise them till we're blue in the face to take cycleways, trams, traffic, buses, or trees with nice benches under them, for the vandals to graffiti over. We can single or double traffic lanes all we want, but at the end of the day every one of the above that is expanded is directly and oppositely to the detriment of the others. And no matter what the Greens say - and to be fair, much of their mutterings ger more criticism than is fair - people will never, ever give up their own personal private transport now that after a century we've got used to it, no matter what the price of petrol, and be they powered by battery, petrol, diesel, gas, paraffin, steam or guava juice. So private vehicles will retain at least some sort of presence in the city for ever. And the population continues to increase which means more of them.
The only show in town in the long run - yes, I know our politicians don't understand what "long" means - is a fully comprehensive underground railway system. Better now when the government has the money than at a future date when we mightn't. We had the world's first commuter railway. No reason why we can't get an underghround railway to match! It needs to connect Swords and Dunboyne north, Maynooth and some of those new places on the Cork line to the east, and Bray / Tallaght / Knocklyon south.