I owe the state of Massachusetts nothing, with one exception; flying into Boston and driving to my destination in NH in the mid '70s and beyond, taught me the laws and the traditions governing the use of roundabouts/traffic circles/whatever they are called in your area. Up there they were well designed and worked fine once you learned the ropes, which didn't take long. While I didn't miss them when the extensions to I-95 bypassed most of them as the years went by, it was a valuable group of lessons. Based on what I learned about traffic circle design in Mass led me to rapidly realize that traffic engineers in MD didn't have a clue with respect to how to design a safe and useful traffic circle, at least when they started showing up in Prince Georges, Ann Arundel and Baltimore counties, and should have consulted with Massachusetts. To this day the stupidest and most dangerous dangerous traffic circle I have ever seen was built in Prince Georges county when I lived there. Up here in south central PA, where I live now (York County), they have put in a couple in the last 5 years or so; they are better than Maryland, but they still should have taken lessons from those that designed them for Massachusetts; though larger in diameter than the really bad ones in MD, they are still too small for a semi to negotiate cleanly, and that's before you get to 53' trailers. At least around here they have put sloped curbs on the inside boundary, so the trailers can easily run up over the inside curb while negotiating them.