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Modern Roundabouts
Arizona Highway Department Arizona has experienced incredible growth since this picture was taken of the old Arizona Highway Department.

Now known as the Arizona Department of Transportation, we have become one of the largest agencies in the state.
Traffic Operations Control Center
Experiencing unprecedented growth during the 1980s and the 1990s, Arizona has become one of the most populous states in the USA. According to the US Census, the state’s population expanded from 1,302,161 in 1960 to 5,130,632 by 2000. This represents 39.98 percent growth in just 40 years.

A sizeable decline does not seem to be on the horizon. In the 2007 Maricopa County Association of Governments Regional Transportation Plan, Maricopa County has grown from a population of 1.5 million persons in 1980, to a population of 3.7 million in 2005. By 2030, Maricopa County is projected to double in population over the 2000 base population, with an anticipated total of 6.1 million people. This means that the region will experience a growth of approximately one million people during each decade.
Modern Roundabouts Such an increase in the number of people migrating to the state has resulted in a dramatic increase in the traffic. And will continue to do so.

More cars, trucks, tractor trailers, moving vans, motor homes and motor cycles -- to mention just a few of the vehicles on our roads and highways -- add up to a lot more traffic.

In November of 2006, The Arizona Republic stressed that “Arizona now has as many registered vehicles, from mopeds to trucks, as people -- including babies. We need a lot of smart solutions to avert perpetual gridlock.”
Did you know . . . the modern roundabout can reduce traffic injuries and fatalities?
Throughout the United States, Departments of Transportation are exploring new methods of traffic control management. The modern roundabout, which is different from traditional intersections, is one of the options.

By understanding what a modern roundabout is, and how it works, motorists are able to travel through intersections easier and safer. Simply stated the modern roundabout is a type of raised intersection with no traffic lights.

Because it is round, some people confuse it with a traffic circle or rotary often referred to as gyratory systems.
The most important difference between the modern roundabout and these “gyratory” involves the

The modern roundabout is being used in hundreds of communities throughout the United States because it is a safer way to move traffic through intersections.
Modern Roundabout in Payson, AZ
Did you know . . . the modern roundabout can increase traffic flow?
Visit the Insurance Institute for Highway Safety (IIHS), check out Research and Stats then locate roundabouts for more information on safety factors. Some of the most important benefits of the modern roundabout are: 
  • Reduces injury accidents by 75 percent and fatal accidents by 90 percent.
  • Increases efficient traffic flow up to 50 percent.
  • Helps the environment by reducing carbon emissions by double digits.
  • Decreases fuel consumption by as much as 30 percent.
  • Costs less than traffic signals and does not require expensive equipment or maintenance.
conflict points in a standard four way intersection
Red dots indicate 32 Vehicle to Vehicle conflict
points in a standard four way intersection.
conflict points in a Modern Roundabout
Red dots indicate 8 Vehicle to Vehicle conflict
points in a Modern Roundabout.
Did you know . . . the modern roundabout helps the environment by reducing fuel consumption and carbon emissions?
In addition to increasing public safety and traffic efficiency while reducing pollution and fuel consumption, the modern roundabout is easy to use. When motorists follow the golden rule -- you never merge; all motorists approaching a roundabout must yield -- modern roundabouts can increase the traffic flow.
Yield “Initially I was somewhat skeptical however I'm supportive of modern roundabouts now. The roundabout at Tyler Parkway is an asset to our community. Drivers just need to follow some simple rules. Yield to traffic in the roundabout, slow down, look left and move right”.    Payson Police Chief Donald Engler
The ADOT Modern Roundabout Video
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2:25 minutes
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Full Length
8:10 minutes
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Modern Roundabout

Video Script (file size: 73KB)

Video Script (file size: 49KB)

Large Vehicles and Roundabouts Video
Large Vehicles Negotiating a Roundabout
9:42 minutes
Play ~ Large Vehicles
The modern roundabout is not built for speed. While the basics are easy remember to go SLOW!

   Slow down to 15-25 mph when entering.

   Let vehicles already circulating go ahead.

   Obey all one way signs.

   Watch for pedestrians, bicyclists, emergency and large vehicles.
The Users Guide offers more details and the following animations will "walk you through" several modern roundabout scenarios. You will experience how easy it is to enter and exit a modern roundabout and what will result with improper use.
Play Choosing the proper lane.
Play Yield to pedestrians.
Play What to do when encountering emergency vehicles.
Play Using the truck apron for large vehicles.
Play Improper lane change results in crash.
Play Wrong assumption leads to crash.
Did you know . . . the highest number of fatalities caused by red light runners occur in Arizona and the Phoenix area?
ntroduced in the early 1900’s in Europe, roundabouts were redesigned as the modern roundabout in 1960. This form of traffic management was introduced to the United States in 1990. For more information about the modern roundabout, check out the History page.   
Modern Roundabouts Modern Roundabouts Modern Roundabouts Modern Roundabouts Modern Roundabouts
Today there are approximately 10,000 modern roundabouts in the United Kingdom, 15,000 in Australia and 20,000 in France. The modern roundabout is also popular in South Africa, Israel, and New Zealand.

Read local newspaper articles on roundabouts. Read national magazine coverage on roundabouts.

The modern roundabout is becoming increasingly popular in the United States. Twenty three states -- including Alaska, California, Colorado and Utah -- have active roundabout programs.

The towns and cities where modern roundabouts have been built -- even where they were initially questioned -- have come to accept this traffic control management option with enthusiasm. Thanks to increased safety and traffic calming as well as aesthetic considerations.

Based on sound engineering principles, safety studies, traffic studies and community input, the Arizona Department of Transportation began to consider the modern roundabout as another tool for intersection and interchange improvements in January 2004.
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