Can you share a roundabout project example and the benefits that resulted from the design?
The recently constructed roundabouts on SR 0981 in Westmoreland County all replace existing stop-controlled intersections. Speed throughout the corridor was a main concern. There was a history of several accidents resulting from high speeds and/or motorists failing to stop. Replacing these intersections with roundabouts has had a speed-calming effect while improving operational delays throughout the corridor. The roundabout designs allowed for improved geometric design while minimizing impacts to sensitive areas such as a church, a cemetery, farms, and new businesses. Read more about this project here.
What is the greatest challenge you’ve run into designing rural roundabouts?
The greatest challenge I have encountered is trying to accommodate oversized vehicles movements, while also trying to maintain a design that meets all safety requirements (Sight Distance and Fastest Path) and minimizes right-of-way and environmental impacts. With the rural setting and the potential for development, we wanted to make sure that the oversized vehicles required for transporting larger construction materials will be able to travel through the roundabouts to get to and from the desired location. Designing for these larger vehicles requires a larger Inscribed Circle Diameter, and larger approach radii. These larger radii often increase the relative fastest path speeds that need to be kept low for overall safety of the facility. Finding the perfect balance, to allow for the necessary turning movement, provide slow enough speeds, and minimize property impacts was a challenging process, but was able to be accomplished through an iterative approach and good communication with all members of the design team.
What role have the public and stakeholders played in the roundabout projects you’ve worked on?
At the beginning, both stakeholders and the public were hesitant to the proposition of roundabouts. Many local farmers were concerned about safety and efficiency while maneuvering large farm equipment through the roundabouts. However, after listening to these concerns, we made sure that along with the agreed upon design vehicle, we also analyzed larger/wider vehicles that reflected dimensions of this equipment ensuring that farmers would be able to safely travel through the roundabouts to get to any adjacent fields that they cultivate.
What do you enjoy most about designing roundabouts?
The best thing about designing roundabouts is the versatility of the design. The design team can work together using sound design principles and good engineering judgement to provide a geometric design for the roundabout that meets the operational requirements for almost any location, while mitigating constraints, and meeting the needs and concerns of the public. I enjoy roundabout design because it is an iterative process, that allows for the designer to use creativity to determine a contextual design based on the user.
