I'm working with pupils from a school that's on the multi-lane, one-way A302 / St George's Road.
This is how it looked down the road at 5pm tonight:
Which brings me to the issue of Junction Capacity and vehicle flow - where different forms of transport are assigned values by transport modellers in relation to one Passenger Car Unit (PCU). So a car is 1 PCU while a cycle is a hugely efficient 0.2 PCUs, as five bicycles can pass through a junction for each car, and a big chunky bus has a PCU of 2 or more.
I'm no transport planner, but what I do know is that a bicycle is always at capacity, whereas a car often has only one occupant and likewise buses (like those above) may be verging on the empty. The conclusion, for efficient use of space in cities, has to be to promote walking and cycling if we want to avoid the kind of urban screw-up images above.