The Department of Transportation published Roundabouts: An Arizona Case Study and Design Guideline Final Report 545 in July of 2003. Sponsored by the Arizona Department of Transportation (ADOT) and prepared by Lee Engineering LLC, the contents of the document reflect the views of the authors who are responsible for the facts and their accuracy.

This report describes the current modern roundabout design guidelines in the USA, and provides a framework for determining where they should be used in the Grand Canyon State.

The design and location of modern roundabouts is part of ADOT’s continual search for new traffic management tools; especially those improving the safety of motorists traveling in a system linking our state to a global economy.

The communities in the state that have incorporated modern roundabouts into their traffic management systems are described below.

Responding to a request from the City of Phoenix, ADOT finished the construction of roundabouts at the I-17/Happy Valley Road interchange in the spring of 2001. ADOT built the modern roundabout to alleviate traffic construction at this rapidly growing location. The construction of these two roundabouts was cost effective compared to the alternatives.

These roundabouts . . . “represent Arizona’s first application of modern roundabout traffic control in this manner . . . The design preparation for and construction of the two roundabouts cost about a third of the estimated cost to build a new overpass bridge and other interchange modifications necessary to accommodate a typical diamond interchange design.” *

Completed improvements to the Happy Valley Road Modern Roundabouts include striping, widening the circulatory roadway to increase capacity, and a modification of entry speeds and circulating speeds.

Scheduled improvements include converting current frontage roads at the roundabouts into one ways.

* ADOT Roundabouts: An Arizona Case Study and Design Guidelines Final Report 545 (Page 1)

Voter-approved, most of the modern roundabouts at McKellips and Brown should be finished by the early part of 2008. Loop 202, is scheduled to be completed in July of 2008. Learning and following the rules of modern roundabouts will benefit everyone.

ADOT is considering building modern roundabouts in other locations as well. For current information about modern roundabouts in Arizona being planned in your community, call your local ADOT District.

Based on sound engineering principals, community input, safety studies, research on other tourism communities, the following modern roundabouts are the choice for these growing communities.

Cottonwood/Clarkdale/Cordes Junction
SR 89A/Cement Plan Road
SR 89A/Avenida
SR 89A/Lisa/Lincoln
SR 89A/Groseta/Scenic
SR 89 Black Hills

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US 89 at Haul Road & the WalMart access

Sedona
SR 179

Southern Arizona
I-19 and Canoa Ranch Road

Wickenburg
US 93
US 60
US 93/Tegner Street

ADOT does not want to create roundabout surprises for the external customer, with that always in mind;