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    and how they came to Kansas:

    My name is James Tobaben and I'm the Chief of Transportation Planning with the Kansas Department of Transportation and formerly, the State Traffic Engineer. I've had a part in bringing roundabouts to Kansas.

    Neither my early driving experience with traffic circles nor what I learned in highway design concerning the operation and safety of large traffic circles made me a fan of circular intersections. However, I began reading articles about roundabouts, which claimed to be something different, even though they looked the same to me at first glance.

    I must admit that at first I had a negative attitude toward roundabouts. It was claimed that they reduced accidents, lowered traffic delay, could accommodate large trucks, and simplified the movement of traffic. Now, a traffic engineer's mission in life is to make traffic operate safely and efficiently, and to make things as simple as possible for drivers. So, I researched roundabouts and where they were starting to be used in the United States. I looked into all their claimed benefits.

    Safety: Roundabouts claim to reduce overall accidents but more importantly, eliminate most injury and fatal accidents. I thought about what I knew about intersection accidents. I knew those accidents with fatalities or serious injuries were usually one of the following types: head-on, left-turn with opposing through, or right angle. That's when I started getting excited about roundabouts, I realized that the design of roundabouts eliminated these three types of conflicts. There's no place in a roundabout to meet another vehicle either head-on or at right angles. The accidents that do occur are rear-end and side-swipe collisions, and these occur at low speeds, therefore the potential for injury is very low. Studies show that accidents involving serious injury or fatality drop by up to 90 percent following the installation of roundabouts. Overall accidents decrease as well. Ok, I gave roundabouts credit for safety, but what about ease of operation, everyone has a story about the time they went through a traffic circle...

    Traffic Operation: Older style traffic circles experienced a number of traffic problems. These include the weaving of traffic that takes place on the circular roadway itself; higher speeds allowed by larger intersection diameters; and, entering traffic had the right of way over traffic in the circle due to the "yield to the right" laws for uncontrolled intersections. The first traffic circles actually were designed with small diameters and worked well under low traffic volume conditions. Problems came as traffic volumes increased. To handle higher volumes, the diameters increased which allowed higher speeds and traffic weaving on the circle itself. With roundabouts, the "weaving" or getting into the correct lane occurs on the approaches to the intersection and not in the circular roadway. Roundabouts' smaller diameter keep speeds low and their "yield at entry" gives the right of way to those drivers on the circular roadway. One question you will ask yourself if a roundabout replaces an existing traffic signal or four-way stop is "Where did all the traffic go?" Traffic signals work by queuing up traffic on one street then letting it go while a queue forms on the other street. Roundabouts handle traffic much more efficiently in most cases. But what about large trucks...

    Large Trucks: My first thought was that large commercial trucks would not be able to negotiate a roundabout easily. I visited roundabouts in Maryland and Colorado, all of which were on the state highway system. All of these intersections carried fairly high overall traffic volumes as well as high numbers of trucks. All of these intersections were designed so that large trucks had no difficulties in traveling through the circular roadway. If you think about it, large trucks often swing a little wide in making a turn. This fits perfectly with the design of a roundabout. But how long does it take drivers to learn to drive them...

    Drivers: The experience in other states, and confirmed here in Kansas, is that drivers have little difficulty in learning to drive roundabouts. Think about coming to a stop sign on a typical four-leg intersection. In order to cross the intersection safely you have to look both to your left and right and find gaps in both those traffic streams that are large enough and that coincide to let you cross. If you are turning left, it gets more complicated as you also must yield to opposing drivers. With a roundabout all you have to do is look to your left and find a gap in traffic that is approaching at a relatively low speed. Once you are in the roundabout, you have the right of way.

    Coming to Kansas: After learning about roundabouts and their differences from traffic circles, I recommended that the Kansas Department of Transportation consider their use in our highway designs. The first ones have been constructed on the I-70 ramp intersections with Rice Road in Topeka and they are working very well (I drive through them at least twice a day). Others are under design or construction at this time. Other cities in Kansas have also recognized the benefits of roundabouts and have installed them at roughly a dozen locations.

    Lessons Learned: Are roundabouts a different kind of intersection? Without a doubt they are, but they do reduce accidents, handle traffic efficiently, and are easy to drive. Give them a try. Unless you enjoy the time spent waiting at a stop sign or at a red traffic signal, I think you will appreciate the way a roundabout moves traffic.

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    Kansas State University
    September 9, 2009