Gyratory traffic schemes, extended one - way systems etc

overly complicated expensive schemes to 'manage' traffic

Spot on, the idea that you have to 'manage' 'traffic' is at the root of the problem here. What people mean by this is either to accept present levels of motor traffic and try to make everything else dependent on current levels of motor traffic, or to increase it and make everything else dependent on the 'requirements' of future, higher levels of motor traffic.