Roundabout - History

History

Numerous circular junctions existed before the advent of roundabouts, including the Bath Circus world heritage site completed in 1768, the 1907 Place de l'Etoile around the Arc de Triomphe in Paris, the 1904 Columbus Circle in Manhattan, and several circles within Washington, D.C., however, the operating and entry characteristics of these circles differs considerably from modern roundabouts. The first British circular junction was built in Letchworth Garden City in 1909. Contrary to modern roundabouts, its centre originally was intended partly as a traffic island for pedestrians. In the early twentieth century, numerous traffic circle junctions were constructed in the United States, particularly in the northeast states. There are many instances of traffic circles in the U.S. that predate the modern roundabout, such as the ones that can be found in Atherton, California.

Although numerous circular junctions existed before the advent of modern roundabouts, the widespread use of the modern roundabout began when Transport Research Laboratory engineers re-engineered circular intersections during the 1960s and Frank Blackmore led the development of the offside priority rule and subsequently also invented the mini roundabout to overcome its limitations of capacity and for safety issues. The rule was adopted as mandatory in Britain for all new roundabouts in November 1966. Unlike traffic circles, traffic approaching roundabouts is normally required to give priority to circulating and exiting traffic (this yield requirement has, however, been the law in the U.S. state of New York since the 1920s) and to eliminate much of the driver confusion associated with traffic junctions and waiting queues associated with junctions that have traffic lights. Roughly the same size as signalled intersections with the same or sometimes a higher capacity, they separate incoming and outgoing traffic, sometimes with pedestrian islands, to encourage slower and safer speeds (see traffic calming).

Initially, they remained much less common in the United States, where limited use began in the 1990s, and they faced some opposition from a population mostly unaccustomed to them. American confusion at how to enter and especially how to exit a roundabout was long the subject of comedic mockery such as featured in the film European Vacation and the television series The Simpsons. By 2011, however, there were about 3,000 U.S. roundabouts, with that number growing steadily. The first modern roundabout in the United States was constructed in Summerlin, Nevada in 1990. This roundabout occasioned a significant amount of "dismay" from residents, and a local news program said about it, "Even police agree, they (roundabouts) can be confusing at times."

Modern roundabouts have since become increasingly common in North America. Carmel, Indiana has more than 77 roundabouts. Its mayor has been active in advocating for the new intersection type and the city hosted the 2011 Transportation Research Board (TRB) National Roundabout Conference.

Roundabouts have had a recent introduction in Western Canada to ease traffic congestion and delays at a great savings when compared to traditional diamond interchanges. Highway roundabout west of Calgary, Alberta, Canada.

As of the beginning of the twenty-first century, roundabouts are in widespread use in Europe. For instance, in 2010 France had more than 30,000 roundabouts.