Gyratory traffic schemes, extended one - way systems etc

I don't see how it does.
The idea that bus journeys save car journeys is based upon the false idea that drivers choose to leave their cars at home and take a bus.

Nobody gets the bus if they have any other alternative.
The only time you'd catch a bus in preference to another form of transport is when the alternative is taking the tube.
If you can walk, cycle, take a taxi or drive you would.

Therefore none of the people taking buses would otherwise be driving. They are on the bus because they have no other choice, save perhaps the tube.

Plenty of people (hopfully decreasing numbers in last few years but still) think the same about cycling. Too poor to even catch the bus etc. Doesn't make it true. some of the people would otherwise be driving.

Incidentally, a direct alternative of taking the tube, I'm more likely to take the tube than bus. But prefer walking and cycling to the bus. This is true for me.