Hi, I?m new to this forum and new to the area. This is sort of my field (yawn). I have only had a quick scan of this thread so sorry if I repeat anything. These blanket 20mph zones are a bit of a gimmick at the moment. Royal Borough of Kingston is currently doing the same, to the dismay of the police. 20mph zones are unenforceable under the current highway act unless the local chief constable agrees to police it, which they haven?t for Kingston?. so probably not for Southwark? Ideally a 20mph zone should be self enforcing i.e. it is difficult for traffic to exceed this limit by the use speed control features usually placed at 60 metre centres. Obviously installing speed bumps, raised tables etcetera on the whole of the Boroughs? roads will be expensive, not suitable for some and controversial on others. So they will end up doing what Kingston has by chucking up lots of signs instead. So if the zone is not enforceable by the police and not self-enforcing what is the point? Sounds like a gimmick to me. I saw someone talking about 50mph limits on dual carriageways. This is not usually done on safety grounds but capacity you can get more traffic through the network at lower speeds at peak times owing to the shorter headway distances required. Take the M25 variable speed limit for example.