Modern Roundabouts provide:
• Low Maintenance: Roundabouts eliminate maintenance and electricity costs associated with traffic signals, which amount to approximately $3000 per year.
• Reduced Delay: By yielding at the entry rather than stopping and waiting for a green light, delay is significantly reduced. A reduction in delay corresponds to a decrease in fuel consumption and air pollution.
• Capacity: A roundabout better handles intersections with a high volume of left turns than a multi-phased traffic signal.
• Aesthetics: The central island provides an opportunity to provide landscaping.
Several factors are crucial to the success of a modern roundabout:
• First, public education: we visited the area a couple of times for open houses to inform the public on the project and give proper guidance on how they are to be driven. This was done for residents of Duvall, Carnation and Fall City, where another roundabout project is being designed.
• Second, advance signing and clear pavement delineation: it is important for us to warn drivers that the roundabout is ahead, and to slow down. By installing median "splitter islands" and curbing, as well as paint striping and signing, we will adequately warn drivers so that they will be at a safe speed prior to entering the roundabout.
• Third, design: It is important for us to get the geometric design right so that vehicle conflicts will be kept to a minimum and so that the traffic flow will be smooth for all types of vehicles.
To ensure that the geometric design will work well, WSDOT utilized the services of Barry Crown, a world renowned expert on roundabouts to help design the roundabout at SR 203 and NE 124th St.
Will this help congestion in the area?
There is significant traffic congestion at the existing intersection, especially during afternoon rush hour for traffic heading east across the valley to SR 203. Another objective of this project is to relieve this traffic congestion.
With a modern roundabout design, entering vehicles always yield to vehicles within the roundabout. This results in a smooth flow of traffic and eliminates the long lines of vehicles seen at many signals waiting for the green light. Traffic continues to move, which reduces the time it takes to get through the intersection.
How will it affect trucks?
The roundabout was carefully designed to handle the truck traffic present on SR 203 and NE 124th. The through traffic movement on SR 203 will be able to handle the immense interstate semi truck and trailer, and the turning movements across the valley are designed to carry a large semi as well as the large dump and pup (gravel hauling) trucks and trailers.