It’s the 5th Annual National Roundabouts Week! We’re highlighting five of our favorite roundabout design projects over the years to celebrate.
From Rotary to Traffic Circle
Powder House Square in Somerville, Massachusetts existed as a convoluted convergence of six two-way streets. Drivers would use the wide circulating lane and large diameter of the rotary to stack side-by-side or find a quick way around slower cars or city buses. Bicycle lanes ended abruptly before entering the rotary, causing an “everyone for themselves” type of intersection with no defined path of travel.
Today, this intersection is a traffic circle with a well-defined single-traffic lane and a separated bike lane around the perimeter. Drivers make their way around the traffic circle slower and are less stressed when navigating between the six streets that make up this intersection. Drivers now have time to acknowledge people biking and have space to stop for them at each crosswalk. Powder House Square is one stop sign (installed for safety reasons) away from being a true roundabout.
The Roundabout Rodeo
As engineers, we do our best with the tools we have at our disposal to calculate the fastest vehicle paths through the roundabout, targeting speeds no greater than 25 to 30 mph. For communities contemplating their first roundabout, a truck rodeo can be a great tool for building support and addressing the concerns of freight haulers, farmers, and other users. Kittelson recently partnered with the City of Stayton, Oregon, to hold a truck rodeo for a roundabout being designed at the intersection of Golf Club Road and Shaff Road. We wanted large vehicle drivers to give it a try, so we reached out to the Fire Department, County Snowplow operators, local industry, The Farm Bureau, and specialty users.
In addition to the public relations benefits of the rodeo, it also helped the engineering team identify a few adjustments to the footprint of the roundabout, that will better suit the community. At the end of the day, the roundabout rodeo was a success. Local leaders and businesses could see the roundabout working, local users tested it, and the engineering team identified design revisions to make it work even better for the community.
The Story of the Temporary Roundabouts After Hurricane Florence
There was no way to fully prepare for the wettest tropical cyclone on record in the Carolinas. Hurricane Florence made landfall in September 2018. A Category 1 storm with a 10-foot storm surge, the hurricane battered the coastal Carolinas with torrential rain and 100-mile-per-hour winds. But the region’s biggest transportation and supply challenges proved to come in the aftermath of the storm.
Among many other safety considerations, in the aftermath of the storm, power outages, road damage, and weather posed driving hazards, particularly at large intersections. Approximately one million people evacuated the North Carolina coastal areas because of the storm, but a significant number of residents decided to hunker down and ride out the storm. Those that stayed had to deal with widespread power outages for nearly a week following the storm, impacting not only residences but also a majority of the City’s 221 traffic signals.
By North Carolina Statute, dark signals become four-way stop controlled. However, many were poorly visible, resulting in compliance and safety concerns. Further, intersections on larger 6 or 8-lane arterials are not well set up to become four-way stops. Collaboration and quick thinking led to a solution that applied traffic engineering rules to organize traffic flow and increase safety with minimal staffing resources.
As it turns out, hurricanes share some characteristics with one of the safest intersection forms – They both move in a circular motion. It was the idea of Officer Eric Lippert, Wilmington Police Department (WPD) Traffic Enforcement Unit, to direct traffic with temporary roundabouts.
The efforts of the City of Wilmington Police Department, City of Wilmington Traffic Engineering Department, Wilmington Streets Division of Public Services, Phoenix Spirit Group, NCDOT, and the fact that this roundabout control had no reported collisions, inspired Kittelson to bring organization to Wilmington’s busiest intersections in the aftermath of the hurricane.
Along with Don Bennett of the City of Wilmington, Kittelson Senior Principal Engineer, Bastian Schroeder, presented this topic during the session “Bending the Learning Curve: Local Agencies Adapting Their Roundabout Implementation Based on Experience” at the 2019 TRB Annual Meeting, sponsored by the TRB’s Standing Committee on Roundabouts.
Thanks to Wrightsville Beach Fire and Rescue for your service and for the foresight to collect this invaluable drone footage!
Eliminating 30-Minute Waits at Braddock Rd/Pleasant Valley Rd
In western Fairfax County, VA, drivers at the Braddock/Pleasant Valley intersection had experienced significant delays for several hours each day. There were numerous constraints to improving the intersection. Kittelson performed an extensive alternatives analysis of several traffic control and lane configuration options, and a 105-foot ICD roundabout was ultimately selected to minimize the footprint of the project while solving the operational issues that plagued the intersection.
The project was successfully led and constructed through a design-build process by the Virginia Department of Transportation, opening to traffic in spring 2016. Since opening, the project eliminated the 30+ minute delays and mile-long queues, significantly improving travel times and the safety and operational performance of the intersection.
Brunswick Forest Retirement Community Safety Retrofit
In Leland, North Carolina the intersection of Brunswick Forest Parkway and Low Country Boulevard was previously a two-way stop control with a lot of unnecessary pavement given the low traffic volume. The neighboring retirement community raised an issue with the crosswalk spanning across 4 lanes of Brunswick Forest Parkway. The uncontrolled crosswalk conflicted with high-speed (40 mph posted speed) vehicle movements. Additionally, there was an island in the center of the intersection which created some confusion for vehicles turning left. The Town of Leland and the Brunswick Forest Retirement Community were eager to remedy the existing conditions of the intersection.
Kittelson developed a low-cost roundabout design for the intersection that meets performance-based design objectives, including vehicle speed control, design vehicle accommodation, and pedestrian accessibility. Our team added value to the project by providing expertise on low-cost construction materials and designed the intersection to include temporary curb and flexposts to keep costs low. Additionally, we built the entire design within the existing intersection footprint, without altering curb and gutter or crosswalk locations. At the Town’s request, the center island was reconstructed rather than expanded for aesthetic purposes.
Kittelson has continued to support the Town and the project by preparing a traffic monitoring plan to assist with determining when regional traffic growth may require roundabout expansion.
To learn more about Kittelson’s design practice, check out our Work page, and don’t hesitate to contact us!