 The Maryland State Highway Administration would like to introduce you to a new type of intersection, the modern roundabout. A roundabout is an intersection having one-way circulation around a central island where entering traffic yields the right of way to circulating traffic. Modern roundabouts have the potential to reduce injury accidents, traffic delays, fuel consumption, air pollution and construction costs. Roundabouts are now flourishing in many countries overseas. Some countries are replacing traffic signals with roundabouts. This method of traffic control is now being introduced in the United States. Although not applicable at every intersection, roundabouts offer a type of control that should be considered when improvements are warranted. This recently installed roundabout in Gainesville, Florida was the first in this country to replace a traffic signal. This tape will explain the characteristics of roundabouts as well as the way they differ from American traffic circles. You may have driven around traffic circles in Washington, D.C. or New Jersey. These are similar in concept to roundabouts but are much larger and have less capacity. The large size of American circles encourages high speeds. Roundabouts are much smaller and have to be negotiated at low speeds. A driver approaching a roundabout slows or stops at the yield line. The driver enters the roundabout when there is an acceptable gap in traffic. This can be done safely because traffic speed is generally below 25 miles per hour. An important difference is the yield at entry rule. A driver entering a roundabout yields to vehicles in the roundabout as these drivers are doing in a circle in Orange, California. In some U.S. jurisdictions, however, the driver in the circle must instead yield to entering traffic. As this picture demonstrates, this is ineffective because when traffic volumes are high the circle becomes filled and traffic is paralyzed. Again, this is not a problem with roundabouts because of the yield at entry rule. There are some small traffic circles in America which have many characteristics of the modern roundabout. Examples can be found in Annapolis and College Park, Maryland and Gettysburg, Pennsylvania. The capacity of an intersection, the maximum number of vehicles that can pass through it in a given period of time, is a key factor as well. Roundabouts, although more compact than big traditional traffic circles, have higher capacity due to their wider entries. Roundabouts can also have higher capacity than signalized intersections of similar size, particularly when the traffic signals have left turn arrows. Moreover, the capacity of a signalized intersection is reduced when traffic stops as the signals change. Concerning safety, reports from countries using roundabouts show a substantial reduction in injury accidents. Here are some reductions in injury accidents reported in Britain, Denmark, Switzerland, the Netherlands, Norway, Australia and France. Roundabouts have fewer accidents for three reasons. First, there are fewer conflict points. The driver who enters a roundabout has to yield to only one traffic movement, the one on the left. By contrast, at a stop sign, the driver who crosses a road has to deal with two conflicting movements, and the one making a left turn has to deal with three. Second, vehicle speeds are much lower, generally less than 25 miles per hour. Lower speeds result in fewer accidents and less severe injuries. Third, decision making is easier for the driver. A driver entering a roundabout has only one decision to make. Is there a large enough space to enter? If not, wait for a gap. Another major safety consideration is the interaction of pedestrians and bicyclists at a roundabout intersection. Reports from European countries and Australia indicate that there is a slight reduction in accidents involving pedestrians. Slower vehicle speeds contribute to this reduction. Reports vary concerning accidents involving bicycles, with some showing increases and others decreases. Depending on the size of the proposed roundabout and the amount of vehicular traffic, special bicycle facilities may be adopted, such as a bicycle bypass or exclusive bicycle lanes. An additional benefit is that roundabouts can often result in less delay than traffic signals. Drivers simply adjust their speed to enter gaps in traffic. If there is no traffic in the roundabout, they do not have to stop. Roundabouts can also be a less costly traffic management solution. Usually the intersections, not the roads between them, are the bottlenecks. Money can be saved if a roundabout is used to increase the capacity of the intersections, making it unnecessary to widen the road between. Also, roundabouts need relatively little maintenance, such as resurfacing, landscaping and sign replacement, while traffic signals cost roughly $3,000 per year for electricity, controllers, lamps and timing plans. Roundabouts have environmental benefits as well. Because roundabouts usually have less traffic delay, fewer cars wait at an intersection. This can help reduce fuel consumption and air pollution. While there are many advantages of roundabouts, they may not be the most appropriate solution when compared with other options at individual locations. However, they are an option that should be considered in many locations. Generally, roundabouts would not be needed at locations where traffic from the minor road can enter the intersections safely and without undue delay. Roundabouts would probably not perform as well where coordinated traffic signal systems are able to minimize delay. Roundabouts should not be used where a nearby signal could back traffic up into the roundabout. There are still questions regarding how well roundabouts compare to other solutions at very high volume locations. In summary, there are five main benefits of the modern roundabout. They are safety. The roundabout is among the safest forms of intersection control. Capacity. The roundabout usually has more capacity with less delay than other at-grade intersections. Economy. Roundabouts save land, pavement and widening between intersections and do not require the energy and maintenance costs of traffic signals. Environment. The modern roundabout reduces fuel consumption and air pollution. Beauty. A well-landscaped modern roundabout can enhance your neighborhood's appearance. We hope this video has interested you in the potential of modern roundabouts. If you would like further information, please write to the Maryland State Highway Administration, Project Planning Division 707 North Calvert Street, Baltimore, Maryland, 21202. The telephone number is area code 410-333-1105.