Access Management Considerations for High Capacity Multi-Lane Roundabout Design and Implementation Prepared By Mark T. Johnson, PE MTJ Engineering, LLC 313 Price Place, #205 Madison, WI 53705 www.mtjengineering.com Hillary N. Isebrands, PE Iowa State University Ames, Iowa 50010
[email protected] 8th National Access Management Conference - “Sustainable Solutions for Transportation” Baltimore, MD July 13 - 16, 2008 Abstract Roundabouts are compatible with many access management principles. The operational characteristics differ from signalized intersections in many substantial ways. This allows for more flexibility that can be of significant benefit when balancing the competing objectives of roadway safety, capacity, and access needs of existing and or proposed land uses. This paper explores examples of the different opportunities that roundabouts can provide and the effects on how the transportation infrastructure is planned and designed. It specifically addresses business access into and near roundabouts, roundabouts in series, and other access management issues compatible with roundabouts in redevelopment, new development and urban constrained environments. Introduction Roundabouts enhance access management strategies. According to the TRB Access Management web site, access management is defined as the: “Systematic control of the location, spacing, design and operation of driveways, median openings, interchanges, and street connections” (AHB70, 2008).” Roundabouts are not only compatible with these access management principles, but Figure 1: Highway 54 in Wisconsin provide the versatility and flexibility often Rapids, WI (Source: MTJ Engineering, needed when balancing the competing LLC) objectives of safety, congestion, user, and access needs of existing or proposed land uses. A narrower roadway cross section is possible with roundabout design (i.e.