[AndrewStephens]

When I moved to Boston I was supersized that people would talk in fear of all the newfangled "rotaries" as they are called here. Roundabouts in general are awesome but Boston has some unique challenges.

Roundabouts work well when there is similar amounts of traffic coming from all directions. In Boston they built some roundabouts where arterial roads meet suburban streets (or country lanes) at odd angles and it causes congestion. There really isn't a great solution for those intersections though - lights would reduce traffic flow.

[ghaff]

It's basically the Route 2-related rotaries. The Concord rotary and the "twin doughnuts of death" as you enter Cambridge. Of course, all those intersections would be nightmares at rush hour however they were designed/configured.