Modern Roundabouts

Moderator: Gene Russell, P.E., Professor and Director Center for Transportation Research & Training, KSU Principle Investigator on 4 research projects on Modern Roundabouts. Kansas Dept. of Transportation Mack Blackwell National Rural Transportation Center Insurance Institute for Highway Safety URL:

Modern Roundabouts Introducing: Tom Mullinazzi, P.E., Professor and Associate Dean College of Engineering, KU, Traffic Engineer Jim Tobaben, D.E., Chief Bureau of Planning KDOT, Former State Traffic Engineer Michael Wallwork, P.E., Principal, Alternative Street Design, Roundabout and Traffic Calming Expert, Teaches Roundabout Design, Former Traffic Engineer, Australia and Florida DOT

Pre Test – “Before” Concerns / Questions

Pre Test – “After” Whether or not these "Before" Concerns & Questions were answered? Additional Concerns & Questions

What are Modern Roundabouts? First what they are NOT Big, old traffic circles or rotaries or gyrotaries Dupont Circle in Washington DC. Arc de Triomphe in Paris Large circles / rotaries in New Jersey (since abandoned)

What they are NOT (cont.) No resemblance to Modern Roundabout large ( > 300 ft. across) high speed based on long weaving sections no priority dangerous high crash rates But opponents of Modern Roundabouts keep trying to compare them

What they are NOT (cont.) Secondly, they are not small circles used primarily for neighborhood speed control –Not primarily an alternate TCD –Think speed bump Little resemblance to a Modern Roundabout But people that "hate" speed control, "hate" roundabouts

Simple & General Guidelines - Michael Wallwork 1.Traffic calming circles are used in local streets only with no splitter islands and no yield signs. 2.Roundabouts range from local street to interchanges, from 12 feet diameter to 20 feet diameter. Have yield signs, splitter islands and operate at low speeds. 3.Traffic circles go from 300 to 600 feet diameter, with merge or stop control, no splitter islands and operate at very high speeds. (Comment on your sheet if you have any problems with these "guidelines")

Difference Between a Large Traffic Circle and a Modern Roundabout - Barry Crown The answer is one of degrees The entry radius is large so high speed entry is possible similar to the high speed circulating traffic Between entries and exits a considerable amount of weaving takes place. …

Difference (cont.) Capacity is determined by the weaving capacity of each weaving section. Weaving at (high) speed is dangerous and uncomfortable. US drivers I have met describe (large) traffic circles as a 'Free for all' after you enter.

Some Typical Concerns 1)Large TrucksLarge Trucks 2)High Traffic Volumes and Emergency VehiclesHigh Traffic Volumes and Emergency Vehicles 3)Large Semi-TrucksLarge Semi-Trucks 3)Football Traffic in Manhattan (predicted to back up 20 miles)

Hutchinson Roundabout A crash in Hutchinson, before the Roundabout was constructed

Bottom Line Benefits 1) IIHS study showed 50 to 89% reduction in serious crashes at 24 sites where 2) Our KSU studies show that at the sites we have studied they are more efficient in terms of average delay, queue length and percent stopped than any other form of intersection traffic control, particularly 4- way stop control and traffic signals.

You may have questions regarding other concerns: Pedestrians Bicycles Education Enforcement Special events traffic

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