Ever seen traffic lights at a roundabout?
yup.
Seen loads of them in the UK and France. Driven on a few 3 lane roundabouts which are quite exciting, but seem to work well. What I did observe was roundabouts seem to work great in areas with few traffic signals around them. i.e. if there is a traffic light 300 yards further on a main road such as what we have with Blanshard then the congestion just moves further along.
But you either love them or hate them. Personally I think they are great. I think its one of these situations where if you have them then you need to have lots so that they become effective.