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I think it will work, Tony, as long as they don't try it out at the really busy junctions in Cambridge.
At some places (e.g. Hills Road / Cherry Hinton Road junction) the volume of cyclists is around 1000 per hour at peak times. [I know 'cos I've had to count them!] With such a continuous flow a cycles, it's hard to see how cars and lorries could ever get across the cycle lanes. (I can't recall ever having monitored traffic flows at the junction where the new roundabout is planned but I suspect that there are far fewer cyclists there)