I have just got a letter in the post from Southwark council, my London borough. They want to institute a 20 mph limit near where I live (Salter Road, SE16), enforced by average speed cameras. It is a busy residential road with a bad accident record etc, etc. Except it is nothing of the sort.
Salter Rd was built in the 1980s as a spine road for the new Surrey Quays development. It has almost no houses on it. As per most modern developments, the houses are all built on side roads and face away from the main road.
So according to Southwark, I have to drive for one mile at 20mph on one of London's quietest non-residential roads to get to my house. They say there have been accidents along it, which is quite true.