West Palm beach, fl had large round abouts installed about 10y ago and I thought that was great, except with little traffic at the time it seemed wasteful in ti

West Palm beach, fl had large round abouts installed about 10y ago and I thought that was great, except with little traffic at the time it seemed wasteful in time navigating and more importantly in space. I think the idea is great though, it's safe and usually gives everyone a fair shot to get moving without much delay.. I'd be interested in knowing how the diameter of the round about is decided on, specifically is it some algorithm based on predicted traffic congestion numbers.