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					                            ROUNDABOUT FREQUENTLY ASKED QUESTIONS

What does a roundabout look like?

                                                                        A modern roundabout consists of a circular
                                                                        pavement section surrounding a center island
                                                                        that separates each leg of an intersection. Each
                                                                        leg of the intersection contains a raised median
                                                                        which is also referred to as a “splitter island”.
                                                                        This splitter island provides a refuge for
                                                                        pedestrians crossing the street and reduces the
                                                                        speed of entering vehicles. It also directs drivers
                                                                        the correct way around the center island, only
                                                                        allowing traffic to make right turns so that
                                                vehicles do not cross paths. Roundabouts
 South Holland, Illinois roundabout designed by Robinson Engineering.

                                                provide more space for landscaping and other
enhancements than a traditional intersection. The size of the roundabout is determined by the
amount of traffic and the posted speed limit.

What are the benefits of roundabouts over a traditional intersection with a traffic signal?
The Village of Tinley Park has received grant funding to help pay for a substantial portion of the
cost of the engineering and construction of a modern roundabout at 183rd Street and Oak Park
Avenue because of the benefits of roundabouts. The benefits include but are not limited to:
    • 90 percent reduction in fatal crashes
    • 75 percent reduction in injury crashes
    • 30-40 percent reduction in pedestrian crashes
    • 10 percent reduction in bicycle crashes
    • 30-50 percent increase in traffic capacity, thereby enhancing traffic flow
    • Reduced vehicular speed through the roundabout, thereby increasing safety
    • Reduction in energy use (auto fuel, electricity for signal equipment)
    • Reduction in pollution (emissions from idled cars)
    • No signal equipment to install and maintain
    • Reduction in noise due to continuous flow of vehicles through the intersection

The most comprehensive study of roundabouts in the United States was completed by the
Insurance Institute for Highway Safety in 2000. The Institute studied 24 intersections, a mix of
urban, suburban and rural environments, which had been converted from signalized intersections
to modern roundabouts. This study reported reductions of 39 percent for all crash severities
combined, 76 percent of all injury crashes and an approximate 90 percent in fatal and incapacity
injury crashes (Crash Reduction Following Installation of Roundabouts in the United States,
Insurance Institute for Highway Safety, Arlington, VA: Status Report, May, 2000).
                                                   The main reason for the reduction in accidents is
                                                   because roundabouts create significantly less
                                                   “conflicts areas” than traditional intersections. A
                                                   signalized intersection has 32 possible conflict
                                                   points between vehicles, whereas a roundabout
                                                   intersection has only 8 conflict points.
                                                   Pedestrians face six conflicts with vehicles when
                                                   crossing each leg of the intersection, whereas a
                                                   pedestrian crossing a leg of a roundabout only
has two possible conflict points with a vehicle.

What is the difference between traffic circles and modern roundabouts? I’ve seen traffic
circles in Europe and they don’t look safe.

Modern roundabouts are quite different from the large, high speed traffic circles built years ago
in Washington, D.C., New Jersey, and other eastern cities as well as in European cities, such as
Paris and London. Designed for high speed entry and multi-lane weaving, the older traffic circles
generally suffered high crash rates and operational problems, causing many to fall out of favor in
the United States during the 1950s and 1960s.

The term “modern roundabout” became popular by 1984 because of improvements, such as
yielding to as opposed to merging with circulating traffic, deflection at entry and low design
speed. Modern roundabouts tend to be smaller than traffic circles and have one or two lanes of
traffic instead of several. In addition to slower speeds and curved entries, advantages of modern
roundabouts also include the fact they are designed using rigorous standards based on specific
turning volumes.

Will it be difficult for new drivers and senior drives to navigate a roundabout?

Two comprehensive studies of modern roundabouts in the United States reported that any
crashes occurring after replacing traffic signals with modern roundabouts did not reflect an
increase in driver age. Although not conclusive, these reports suggest that modern roundabouts
do not pose a problem for older or younger drivers.

Can a large truck or semi get through a roundabout? How about fire trucks and other
public safety vehicles?

Modern roundabouts are designed to accommodate emergency and other large vehicles. They are
typically designed to hold the type of automobiles that are allowed on the road. For example, if
the roundabout is on a highway route, it will be designed with a geometry that allows for semi-
trucks and trailers.

If you are in a roundabout and you see an emergency vehicle, pull over as far to the right as
possible and let the vehicle pass. Whenever possible, completely clear the modern roundabout
and pull off to the side. Any time lost by an emergency vehicle navigating the modern
roundabout, where speeds are never higher than 15-25 mph, will only be a few seconds.
I’ve seen a lot of roundabouts in Florida – are they suitable to snowy conditions of the
Chicago area?

There are many modern roundabouts already in place in Michigan, Colorado, and New York
where snow is a constant concern. The center island and adjacent parkways can be utilized for
snow removal operations. Roundabouts are safer that traditional intersections in snowy/icy
conditions because vehicles cannot cross through the intersection and crash into each other.

What resources can I read to find out more about modern roundabouts?

   •   Roundabouts: A Direct Way to Highway Safety.
       U.S. Department of Transportation, Federal Highway Administration

   •   Kansas State University, Center for Transportation Research and Training. http://www.k-

   •   Modern Roundabouts: The Website.

   •   Insurance Institute for Highway Safety.

   •   Illinois Center for Transportation.