[d43594]

Gloucestershire in the UK have a habit of putting traffic lights on roundabouts which as you can imagine completely defeats the point of one. A round about automatically prioritises traffic based on demand. This combination of two contradictory solutions is the work of the devil.

[barrkel]

Roundabouts need traffic lights if any exit has a continuous stream of traffic; it starves the entrance immediately before the exit. If there's much traffic entering before a popular exit, it can easily get backed up. I've seen several roundabouts get traffic lights, or get converted back into a traffic light junction, because of this, as traffic patterns changed.