The Modern Roundabout - the right choice for many locations!

Success unlocks their potential

The first few modern roundabouts were able to solve awkward intersections that were previously unsolvable, helping them earn a great reputation. With planters and monuments, they are attractive and help create a sense of place. They also calm oncoming traffic, which combined with far fewer conflict points, and have helped them prove to be very safe intersections for both vehicles and pedestrians.

Single-lane roundabouts have significantly better capacity than a four-way stop. They also work well as replacements for lower-volume signals. A mini-roundabout appears very nearly the same as a regular residential intersection, but has a painted or small raised island in the center encouraging vehicles to use the right-of-way rules of a larger roundabout, but with a lower cost and smaller intersection footprint. Single-lane and mini-roundabouts are great choices for residential areas.

There are only a few multi-lane roundabouts, but they are proving able to serve similar volumes as what might occur when a minor arterial meets with a major collector. In extremely high volume environments, the size of the roundabout required for high efficiency may be prohibitive. But fortunately there are other Alternative Intersections! One such option is a Bowtie, a sub-category of the ThrU-Turn intersection style. With a Bowtie, rather than put a roundabout in the center of a primary intersection, roundabouts or ellipsabouts are off-set between 300 and 700 feet. Left turning traffic first travels Through the main intersection, makes a U-turn using the roundabout, then makes a Right. Hence the name ThrU-Turn, for Thru-U-Right. A Bowtie system with two small roundabouts can attain significantly more capacity than a single larger roundabout in the center of an intersection.

How did these become popular? Where can I learn more?

RoundaboutsUSA is among the most popular repositories of the history and current status of the use of roundabouts. They report that as of 2010, there are over 2,500 known sites in the USA, with many more mini and sub-division sites. They note that the basic changes that define a modern roundabout were implemented in England in about 1963. Leif Ourston was the first to bring them to America, opening one in 1990 as part of the Summerlin development in Las Vegas, then opening the first roundabout freeway interchange in Veil, Colorado. They took off in Utah around 1996. From these few western states they have propagated across the nation and are experiencing a rejuvenation across the world.

Roundabouts are "Alternative Intersections"

InnovativeIntersections.org provides a wiki-type record of the locations and attributes of interesting roundabouts as well as other design styles. Because there are so many roundabouts, it is not practical nor desirable to record them all. Instead the focus is on  some of the more interesting applications of roundabouts.