Modern roundabouts provide 90 percent reduction in fatal crashes and typically carry about 30 percent more vehicles during periods of peak traffic volume
Contributed by Jim Blount
It hasnt received much publicity, but a new configuration of traffic management has been introduced at a pair of intersections by the Butler County engineers office. For two years, drivers at two locations have successfully maneuvered through modern roundabouts. There are plans to convert other sites, according to Greg Wilkens, Butler County engineer. Neighboring Hamilton County also is planning roundabouts.
In Butler County, single-lane roundabouts are at (1) Hamilton-Mason, Liberty-Fairfield and Vinnedge roads in Liberty Township and (2) Lakota Drive West and Eastridge Drive in West Chester Township.
Familiar to anyone who has driven or traveled in Europe, the rotary systems have been scarce in the United States. When tried about a century ago, U. S. motorists found roundabouts confusing and contributing to gridlock and accidents instead of easing traffic flow.
Some sources claim that New Yorks Columbus Circle, opened in 1904, was the first -- or, at least, the most publicized -- traffic circle in the U. S. That was in the era when horse-drawn vehicles were still in the majority.
By 1950, most of the American roundabouts had been replaced because they couldnt handle high traffic volumes. Europeans -- instead of eliminating the rotaries -- retained and refined them. Now the improved design is emerging in the U. S.
There were several problems with the old U. S. roundabout form. One was that entering traffic had the right-of-way, causing gridlock when there were numerous vehicles in the circle. Stop signs or traffic signals regulated vehicles entering the roundabout, which reduced capacity and flow. Another complication was permitting parking within the circle. Pedestrians also contributed to the confusion -- and safety perils -- because crosswalks usually radiated from the central island.
The major complaint from U. S. drivers in the early decades of the 1900s was inconsistency. There was no uniformity in right-of-way rules. Roundabout regulations differed from state to state and within states. In some situations, for example, vehicles entering on a north-south line had the right of way over east-west traffic, or vice versa.
In others, with low traffic volumes, there were no signs to direct drivers and pedestrians. It was assumed courtesy and common sense would prevail.
Other difficulties were caused by large diameter central islands and the number of lanes. Both factors tended to increase the volume of vehicles within the system and the chances for accidents.
In England -- where the circle system was known as a gyratory until officially renamed roundabout in 1926 -- traffic engineers sought improvements instead of abandoning the rotary intersections.
The British began introducing changes in the 1960s. The modern roundabout began in the U. S. in the early 1990s, mostly in Utah, Colorado and Nevada. By 2009, there were about 2,300 modern roundabouts in the U. S.
U. S. drivers of the early 20th century -- whose gripes led to elimination of many circles -- would see many differences in the modern design and procedures.
Yield-at-entry is now the No. 1 rule for drivers. That means vehicles in the circle have the right of way. Those approaching the roundabout also are expected to slow down and look for pedestrians in the crosswalk.
The driver approaching a modern roundabout will face a yield sign -- not a stop sign. If there are no vehicles approaching from the left and no pedestrians, the driver may turn right. "You now have the right of way," according a brochure available from the Butler County engineers office.
Some nomenclature describes the roundabout entry process as "off-side priority" or the "yield-to-left rule," but they mean the same thing: yield to traffic within the roadway. Wait for an appropriate gap before proceeding into the circle.
"Once you have entered the roundabout, proceed counter clockwise [right] to your exit point," advises the BCEO guide. "As you approach your exit, use your right turn signal," but be prepared to yield to pedestrians in the crosswalk.
Pedestrians dont use the central island in the modern roundabout. Instead, crosswalks are on the intersecting streets. The system also includes what is called a "splitter island" in engineers lingo. That is a safety platform located in the middle of each intersecting street.
The BCEO says "when comparing a roundabout to a signal, studies show the roundabouts provide a 90 percent reduction in fatal crashes, 75 percent reduction in injury crashes, 30-40 percent reduction in pedestrian crashes and 10 percent reduction in bicycle crashes." In traffic capacity, BCEO reports "roundabouts typically carry about 30 percent more vehicles than similarly signalized intersections during peak flow conditions."
For more information and graphics on Butler County roundabouts, go to the Internet at http://www.bceo.org/departments/engineering/traffic.html.
2010 Articles >