STH 145 Interchanges with USH 41 and USH 45 - Richfield, Wisconsin
The Wisconsin Dept. of Transportation deemed it necessary to improve STH145 to accommodate traffic volumes that were expected to increase from 6,000 to 18,000 vehicles per day based on the recent construction of a Cabela’s store, outparcels and future development.
The bridges over U.S. Highways 41 and 45 were a strong consideration in the decision to construct roundabouts on STH 145. The Wisconsin Department of Transportation wanted to retain the two, 34-year-old bridges that were designed to last 75 years. In addition, the bridges were too narrow to accommodate the right- and left-turn lanes that were necessary to upgrade STH 145 with traditional intersection types.
A system of five roundabouts was chosen as the preferred design alternative to allow the bridges to be redecked in lieu of total replacement, saving nearly $2 million in construction costs. The project’s design and construction were completed in a compressed three-year schedule (November 2006 to November 2009) required by the Wisconsin Department of Transportation.
The STH 145 project involved many challenging aspects and innovative design solutions, a few of which are discussed below.
Application of New Design Techniques for Multi-Lane Roundabouts Ensure Safety, Efficiency
R.A. Smith National recognized an opportunity to use design concepts that were relatively new in the United States at the time of this project, to ensure safe and efficient roundabout operations. One such technique was the use of spiraling central islands and pavement markings to eliminate the need for drivers to change lanes within the circulatory roadway.
Development of a Unique Design Vehicle Accommodates Needs of Local Business
Innovation was demonstrated by the R.A. Smith National design team in the development of a unique design vehicle used to model a business owner’s 99-foot truck/trailer’s paths through the roundabouts. During the public involvement process, R.A. Smith National was approached by a local business owner concerned about the ability to navigate an oversized truck/construction trailer through the roundabouts. R.A. Smith National met with the business owner to take measurements of the vehicle, determine the location of the axles and pivot points and collect additional information. This data was then used to create a unique design vehicle in the AutoTurn software to model this 99-foot truck/trailer’s paths through the roundabouts. Using this model, the roundabout designs were adjusted to accommodate this oversized vehicle.
First-of-its-Kind Roundabout Design Sets New Standards for Engineering Industry
STH 145 was the first roundabout project of its kind in the State of Wisconsin with five closely-spaced roundabouts constructed within a 0.6-mile corridor. This scenario is unique to roundabout design in Wisconsin and the state engineering industry. This atypical situation required analyzing and designing the roundabouts as a system, not just individual roundabouts, to ensure correct lane assignments and efficient operations throughout the corridor.
At the time of this project, there were no examples to reference for staging the construction of a corridor with five roundabouts, as most roundabout projects were constructed with road closures. R.A. Smith National created a first-of-its-kind model for the engineering industry.
The use of concrete pavement on roundabout projects was not common at the time of this project. New ground was tread in developing concrete jointing plans for circular intersections.
As WisDOT develops similar corridors with closely-spaced roundabouts, the STH 145 project will serve as a standard for design of these roadways, constructing roundabouts while keeping the road open to traffic, and jointing of concrete pavements in roundabouts.
STH 145 Wins Multiple Design Awards
R.A. Smith National has won the following state and national awards for the design of the roundabouts at STH 145:
• Best of State, Engineering Excellence Awards, American Council of Engineering Companies (ACEC) of Wisconsin, 2011
• National Recognition Award, American Council of Engineering Companies, 2011
• Excellence in Highway Design, Consultant Rural Design, Wisconsin Department of Transportation, 2011