The in basket: Robert Balcomb of Silverdale e-mails to say, “I have wondered about the compared cost of the roundabouts at CK Junior High, at Silverdale Way and Newberry Hill, and at Manette, versus stoplights there instead. I think stoplights would have been considerably cheaper, involving less construction time, and be less problematic.”
The out basket: Two of the three spots Robert asked about were Kitsap County projects, so I asked county public works for a comparison.
Jeff Shea, traffic engineer for the county, said, “Discussion papers I’ve reviewed talk about the costs of signal hardware being offset by the additional cost of right-of-way needed for a roundabout.
“Although cost is a major factor when making the decision on what type of intersection control to use, there are many other factors that play into the decision. Also, while construction costs may be similar, the ongoing costs of maintenance and electricity for signals are also a consideration when making the choice between signals and roundabouts.
“Each intersection has unique characteristics, and both signals and roundabouts have pros and cons, depending on the application.
“Collision rates are generally lower in a roundabout than at signalized intersection, and the severities of the collisions are usually minor. Fewer vehicles are required to come to a complete stop in a roundabout, and because of slower speeds they provide some traffic calming benefits. Reduced speed through the intersection allows for safer pedestrian crossing in most instances.
“They do take up a lot of space, and present some challenges to bicyclists. In some instances they restrict access to adjacent properties and some multi-lane roundabouts have a learning curve (for drivers) before they achieve optimum efficiency.
“Traffic signals take less space and can generally be built within existing rights-of-way unless additional lanes are constructed. In many applications, signals can be programmed to allow continuous progression of traffic flow. They can be programmed to facilitate the majority of traffic flow and usually have minimal affect to access property adjacent to the intersection.
“Signals require regular maintenance and are more expensive to maintain. Signals are susceptible to power surges and outages and create a challenge for motorists when they are not working properly.
“In the end, it comes down to what works best for the particular intersection that is improved. Traffic signals are well understood and good choices for certain locations. Roundabouts are gaining in acceptance, and are being used at many intersections traditionally served by traffic signals. In each improvement project we consider the alternatives and choose the one that our studies conclude are likely to be the most effective.”