High Capacity

This roundabout is located near Stoke on Trent (video reversed), England at an interchange between and freeway and a divided arterial.  It is a large two-bridge roundabout that carries approximately 6000 crs per hour with four lane entries.  Note the platooning effect of entering traffic, particularly in the shadow of the larger trucks.  In the U.S. this roundabout would be crash prone because drivers would ne know when to yield, especially with the flat entry angles.


Another off-ramp entry to a roundabout, this time in Arizona.  Note the exit has two lanes tapering to one over a 15:1 merge taper.  This complies with AASHTO speed and lane drop criteria but most designers would not think it possible.


The Avon, Colorado roundabouts were the first corridor of U.S. roundabouts.  The video speeds up at one point to illustrate how without traffic signals the flow is continuous versus stop-start or on-off.  Even the large truck moves through the systems without much delay.


This moderately sized three leg roundabout was modified to add dual partial right turn lanes on each entry.  It is located in Cannock England (video was reversed).  Previously the entry had two lanes but no partial rights.  Notice how flat the entry angles are yet drivers are respectful of priority rules.


The following are of a pair of closely spaced roundabouts at Lee Road and Michigan SR23.  Note the lack of overlapping queues from each roundabout.  This pair suffered from poor approach sign design and an overabundance of markings.



Vail interchange roundabouts that helped start the roundabout revolution in the States.  They were the first of roundabout interchanges and had multi-leg and multilane entries.  Development access was not compromised and the undercrossing of I-70 did not need to be widened. (wide nodes and narrow roads concept).  Note that the circulatory roadway doesn’t need lane lines even after 15 years of operation.  They were tried in 2011 but allowed to wear off because they caused more problems than they solved.  There is no need for a truck apron if circulating lane lines are not needed.



The roundabout at the University of Utah is famous for the railway through the middle of it.  Note all the gates and hardware.  It works well because the traffic volume is low and the length and speed of trains is small.  These are in parts of Europe also and are sometimes called hamburger roundabouts.


Still one of only a dozen or so three lane roundabouts was opened in Michigan in 2004.  The pedestrian traffic is sparse.



These videos are high capacity three lane entry roundabouts located near Green Bay, the home of the football champion Packers.  The jointing and lane lines are coincident to improve guidance.  Both have rolled crown cross-sections for the circulatory roadway.  Both have moderate pedestrian traffic in peak periods.  Both roundabouts replaced traffic signals.



The following videos show miscellaneous two lane roundabouts in various settings of urban land use with nearby access. 



This video shows a rural two lane roundabout with heavy trucks and a mix of other users.  It has approach speeds in the range of 55mph.  When the Amish community was asked how they felt about the roundabout their general consensus was that the county could do what it needed and their people would adapt.  The roundabout replaced a traffic signal and reduced injury collisions by 60%.  Even with actuation lops the horse and buggy could not trip the signal in the past.  With the roundabout, vehicle crossing speeds are comparable to horse and buggy speeds.


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