State & Ellsworth Roundabout Project

The Washtenaw County Road Commission, in partnership with the City of Ann Arbor and Costco, plan to move forward with the construction of a modern roundabout at the intersection of State and Ellsworth Roads. This intersection is located at the border of the City of Ann Arbor and Pittsfield Township. The Road Commission will design and construct the project, acquire all necessary permits, and provide the construction engineering services.

Tornado Hits DexterConstruction of the roundabout is expected to begin in March or April of 2013 and be completed by Labor Day and U of M’s first home football game.

The primary purpose of this intersection improvement project is to mitigate projected traffic congestion created by the new Costco development. This development is located behind Tyner Furniture on Ellsworth Road, west of State Road.

“Traffic in the area is heavy now and is expected to increase by 20 percent over the next 20 years,” Mark McCulloch, Project Manager, stated. With the amount of current traffic and the anticipated increased traffic resulting from the new Costco development, traffic studies confirm the roundabout to be the best solution to handle the continued growth. "The current flow rate is around 3,500 cars a day. The roundabout will be able to handle 5,000 cars a day," said Road Commission Managing Director Roy Townsend.

In addition to reducing traffic delays, modern roundabouts enhance safety for motorists and other users of the intersection by reducing speeds to less than 25 MPH and eliminating direct left-turns. The latter is achieved by forcing drivers to circulate around the central island. This circulating movement eliminates high speed, right angle and left turn/head on collisions that occur at traditional signalized intersections. Roundabouts also significantly reduce the amount of pollutants released into the atmosphere from idling vehicles. At signalized intersections, drivers typically wait 20 seconds or longer for the light to turn green. Since the entry control at modern roundabouts utilizes the “yield to left” principle, drivers spend less time idling their vehicles prior to entering the intersection.

As stated by a 2011 report from the Insurance Institute of Highway Safety, 23 intersections that were converted into roundabouts experienced significant declines in accidents. Total crash frequency fell by approximately 40 percent; injury crash frequency fell by approximately 80 percent; and fatal crash frequency fell by approximately 90 percent.

Tornado DebrisA detailed study of the State and Ellsworth intersection determined a two-lane roundabout would best accommodate the traffic projected at the intersection.

The design of the roundabout is 150 feet in diameter with all intersection approaches having at least two lanes to accommodate traffic entering and exiting. The southbound approach on State Street includes a third lane allowing anticipated high volumes of right-turning traffic onto westbound Ellsworth in order to bypass circulating traffic.

Other features include non-motorized paths in all intersection quadrants that connect with the existing sidewalk system and new on-road bicycle lanes, street lighting, and underground electrical conduits for the future addition of HAWK or Rectangular Rapid Flashing Beacon signals at the crosswalks should they be required.

Although the Road Commission intends to keep the intersection open to traffic during construction, delays will occur to motorists who must use this intersection. Motorists are encouraged to use alternate routes during construction if possible.

The total project cost is estimated to be about $2.5 million. The Road Commission has secured a Congestion Mitigation and Air Quality grant from the Federal Highway Administration (FHWA) in the amount of $1.4 million. Costco contributed $500,000 that will be used for other miscellaneous costs such as design, right-of-way acquisitions, and construction inspection. With the exception of any landscaping, decorative concrete, or public utility upgrades, the Road Commission and the City of Ann Arbor will share the remaining costs for the roundabout. The city will be responsible for costs associated with public utility upgrades.

The Road Commission held a public information meeting on February 29 at the Pittsfield Township Hall to unveil the project to the public and answer questions from audience participants.Road Commission staff also met with various stakeholders and public safety personnel prior to this meeting to brief them on the upcoming project and address their concerns. A second meeting is planned prior to the start of construction that will cover more of the project details.

For additional information about roundabouts and the navigation of roundabouts please refer to our website’s information on Modern Roundabouts located by clicking here ».

For additional questions specific to this project, please contact Mark McCulloch at 734-327-6679, or e-mail at