There’s a resource on roundabouts and emergency services available on the U.S. Department of Transportation website. The SS4A Technical Assistance Center's general advice to agencies pursuing their first roundabout is to go above and beyond the norm for coordinating with Fire and Emergency Medical Services, including them in the preliminary planning and design, all the way through construction and opening. It sometimes helps to hold a “test drive” where the basic geometry is laid out using cones and sandbags in a parking lot or field, having the Department drive through and observe the results, and then use that information to tweak the design. There are also design details that can make a huge difference, such as truck aprons and sloped curbing.