Roundabout Fever Is Going Around
March 04, 2006
Chances are that a roundabout has been constructed or is being considered somewhere near you. Twenty years ago, this would have been highly unlikely. “Traffic circles” have been in use for over 100 years in the United States. However, the “modern roundabout,” common in other parts of the world for 40 years, has only been introduced in the past fifteen years.
Today there are well over 500 roundabouts across the United States. While this is still a frac-tion of all intersections – with over 300,000 traffic signals and even more stop-controlled inter-sections – the number of roundabouts is growing exponentially. Between 50 and 100 round-abouts are being built every year in the U.S.
What caused this recent surge in interest in roundabouts? Roundabouts are proving to be ef-fective at addressing some of the vexing problems that transportation professionals struggle to solve. Transportation professionals use many techniques to manage intersections with large numbers of accidents, particularly on high-speed facilities; stop signs and traffic signals are generally used to assign right-of-way. However, accidents still occur at these intersections, most commonly as a result of driver error. Lee Rodegerdts who leads KAI’s national round-about practice notes, “while roundabouts cannot prevent driver error, the roundabout design prevents drivers from colliding at the angles and speeds that cause the most severe injuries and fatalities.”
Transportation issues also occur frequently at congested locations. Roundabouts have been used at ramp terminal intersections at freeway interchanges with great success, providing dramatic improvement. The roundabout design can often increase capacity without widening the bridges that separate the freeway from the crossing arterial street. Beyond the potential to address these problems, people are often excited about the round-about's potential to enhance the aesthetics of their environment. Roundabouts offer unique opportunities to use landscaping and other gateway treatments to define or add character to a neighborhood or commercial district.
The Federal Highway Administration and state agencies are developing guidelines, training, and support services for roundabouts. Ongoing research and publications detailing successful and not-so-successful projects are also helping to demystify the roundabout. The greatest fac-tor, however, is that members of the general public are becoming familiar with roundabouts, either by using one in their community or encountering one through travel. As a result, agen-cies are becoming more able to consider roundabouts as they explore transportation solutions.
The key to understanding a roundabout is to recognize that a roundabout is just another type of intersection. Roundabouts yield significant safety and operational benefits while helping to enhance our urban environment.