Roundabouts vs. traffic signals

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.”


6 thoughts on “Roundabouts vs. traffic signals

  1. Two state transportation departments (NY and VA) along with British Columbia and Alberta boast “roundabouts only” policies–roundabouts unless unfeasible (i.e., over 90% of typical intersections). Why? Anything but a roundabout generates serious injuries at a 900% greater rate (Insurance Institute of Highway Safety study of US roundies 2001). A fatality occurs once a year per 135 signals, about six die at signals today while the French roundabout rate (over 30,000 roundabouts there) would drop that would drop that to about one.

    Plus roundabouts do everything else better–less delay for all users, less energy use, less pollution, sharply increased walker safety, and less scenic blight, etc.

    Tony Redington

  2. No where does he talk about the cost to MOTORISTS. IMHO (and others) stop lights (not traffic signals) are THE reason America has to import foreign oil. And that’s just the cost of fuel. Then there is wear and tear to vehicles, air pollution (gas engines emit virtually no pollution when traveling at highway speeds) and,,, time. We spend a fortune of our time stopped for lights. Did I mention accidents? Gridlock?

  3. I lived in England for two years where roundabouts are utilized a lot. One of the detractions noted above are for bicyclists and pedestrians. The British overcome that at many roundabouts by having either overhead walkways like in Ghorst or pedestrian tunnels under the roundabout. I found the tunnels to be most useful when running or riding a bike as the slopes were significantly less to go a 10-12 feet down as opposed to the 20+feet up that is needed to allow trucks to get under the crosswalks. Also provided shelter if the rain was really coming down. We should consider those options when building roundabouts.

  4. Stop lights are just another way to play to stupid drivers who can’t figure out a roundabout. If you can’t figure it out you shouldn’t drive. But there is too much money for a municipality to make at intersections with stop lights for them to do away with it in most places.

  5. I love roundabouts. The new one at lake Flora road has made that area alot safer. It is a very busy area, and now people have to slow down, its great!!!

    Now we need more lighting in this area, There should be lights at corners to county Roads so you can see where you are turning, and if there are any people on the corner, because for some reason people walk around in the dark in dark clothes and you can not see them when you are making a turn onto a road that has no light.

  6. Will someone please add Round-A-Bout questions and training in how to SLOW down for them and use them properly to driver training and licenseing. The one in Gig Harbor is horrible at Burnham Dr and those coming down the hill come very close many times to hitting those wishing to get to Canterwood Dr.

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