Thursday, October 1, 2026
.jpeg)
| A strict state law passed three decades ago was designed to contain high density growth in Washington state, altering the fabric of our communities. In yesterday’s segment, the reality of how local government planning activities are dominated by adherence to the requirements of the state’s Growth Management Act was described. In today’s article, the reasons underpinning transportation planners’ love affair with roundabouts will be explored. |
In 1985, the farcical comedy "National Lampoon's European Vacation" was released. Actor Chevy Chase played the lead character, Clark Griswold, who in one scene finds himself in a rental car endlessly circling a roundabout in London.
The sight gag was humorous because while many Americans knew that roundabouts were in use elsewhere in the world, not many drivers had experienced them here and they seemed, well, weird. Many drivers view roundabouts with hostility to this day. However, love them or hate them, you’ll likely see a lot more of them across Thurston County in the years to come.
While the City of Tumwater was able to put off redesigning the traffic-clogged intersection of Capitol Boulevard and Trosper Road for many years, the clock ran out in 2015. The design approach that was eventually adopted to improve the crossing was to install a roundabout.
In fact, three roundabouts were built virtually atop each other as part of the redesign. But why were roundabouts chosen and why are they likely to become so common across the county in the years to come?
Few roadway design choices are more controversial than the one to install a roundabout. Yet, traffic planners love them. As of 2015, of Tumwater’s 69 major intersections, five were configured as a roundabout.
But tentative plans enshrined in the city’s 2016 Transportation Master Plan have identified an additional 23 primary intersections that may be converted to this format. Separately, Olympia has identified seven intersections proposed for conversion to roundabouts just on Harrison Avenue on the Westside! The key impetus for moving to this design approach is safety.
Consider the prototypical urban intersection of Cooper Point Road and Harrison Avenue in Olympia. Two lanes of traffic enter the intersection from all four road segments and two more lanes exit. An additional four left turning lanes complete the design with signal lights sequencing flows.
Roundabouts tentatively planned for Harrison Avenue in Olympia
Courtesy City of Olympia
You may have crossed an intersection of this layout thousands of times over your lifetime. However, at every point where traffic can meet other traffic traveling on a different path, there is an opportunity for something to go wrong. The U.S. Federal Highway Administration calls these “Vehicle conflict opportunities.” And a standard signalized intersection generates at least “32 potential points of conflict.”
If every driver does what they are supposed to, none of these conflict opportunities become a problem. But, of course, that doesn’t always happen. At least nine collisions occurred at the unremarkable Cooper Point and Harrison intersection just last year.
Collisions at intersections are more frequent than many people recognize. Last year, there were 4,196 collisions at Thurston County intersections, about one accident for every 75 residents. Of those collisions, 55 resulted in serious injury. And 11 resulted in at least one fatality.
Not surprisingly, traffic planners focus on any roadway design approach that can make road crossings safer. And the best way to make intersections safer is to slow vehicles down.
Looking again at the intersection of Cooper Point and Harrison, both roads have a posted speed limit of 35 miles per hour. A vehicle accident at that speed can generate a deceleration force of over 60g. And that presumes you're actually driving the speed limit (and wearing a seat belt).
That’s the same as being hit by something that weighs 60 times what you do. Pedestrians hit at 32 mph have a 25% chance of being killed. Driving your 2-ton automobile exposes you and the people around you to significant risks every time you cross another road.
Roundabouts are a natural draw when planning an intersection redesign for four primary reasons:
The four advantages of a roundabout typically generate big safety wins. Studies have shown 35% fewer crashes, 76% fewer injuries, and 90% fewer fatalities in intersections controlled by a roundabout compared to intersections handling the same traffic levels controlled by signal lights.
It’s no wonder the Washington State Department of Transportation, “Encourages the implementation of roundabouts.” Fewer accidents, far fewer injuries and fatalities, more efficient traffic flows, and pressure from the state all combine to make installing a roundabout a default choice for traffic planners.
While many drivers, especially people unfamiliar with their usage, are apprehensive about roundabouts, that fear often dissipates after they start navigating them.
According to the Washington State Department of Transportation, “After driving roundabouts, the number of people who favor them” increases from 31% to 63%.
But if you don’t like roundabouts, don’t worry: you’re not alone. The same study still showed 15% strongly opposed, even after using them. Perhaps the roundabout-phobic should be thankful that no traffic engineer in the United States is considering replicating the Magic Roundabout that has been operating for decades in Swindon, England:
Several design choices were available to the traffic planners at the City of Tumwater when they were redesigning the intersection at Capitol and Trosper. However, the safety benefits and efficiency of roundabouts made the choice of that approach almost inevitable.
All three intersections that were eventually part of the project used this design approach. And the majority of intersections set to be rebuilt across the county in the coming years will likely be roundabouts as well. Let’s hope Clark Griswold finally learns how to exit them.
In tomorrow’s segment: "The three ring circus” comes to town
Read previous installments in this series on The JOLT News website:
Part 1: The Creation of Washington’s Growth Management Act
Part 2: How the GMA Impacts Local Government Transportation Initiatives
6 comments on this item Please log in to comment by clicking here
SAlexander
The need for roundabouts in Tumwater has become an insane thought. It seems staff, whose salary we, the people are paying, just sit around wondering how they can make someone's life more miserable by putting in a roundabout. I agree with some of them and think others are just to keep people in their jobs but doesn't really do anything for the public. When I moved here, I was impressed with Tumwater and the people living here. Not so much anymore.
Sharon Alexander
Wednesday, June 17 Report this
someoldguy
As a roundabout fan, I suggest that Harrison NOT add all those roundabouts. Just keep one or more select signals please. Those signals can give some form of operational control to the adjacent roundabouts and side street stops when dominant flows ...get too dominant and you want to serve those side streets. Those mainline gaps caused by just one signal that phases can work wonders on downstream yield or stop controlled intersections. This is the art of transportation engineering, not the science of it. Not to pick on PEs but we need a planner in the room as well when making these corridor intersection control schemes. Also, knowing the traffic patterns far beyond hourly volumes is the key and that takes more than data - it takes time on the sidewalk watching - through all the seasons. Which intersection(s) to keep as a signal to help all the roundabouts, stop controlled intersections, pedestrian crossings, etc? It would take me a lot of effort to identify but thankfully, multiple agencies have experts that should be able to weigh in effectively. Just don't use Synchro - use Sidra with Networking and then adjust the volumes for various scenarios until you're sick of it. When you feel comfortable, then load it with more demand until it breaks again so the development community will understand how many more trips the updated corridor can take with this new safety and capacity design. That'll inform the agencies about zoning potentials and such and that'll help optimize the land use and density of the corridor. And that optimized commercial tax base could take some of the burden off residential property taxes?
Wednesday, June 17 Report this
paisleytie
I wish we could get a roundabout on Capitol Way South before the bridge over I-5. I'm new to the neighborhood and in a scant 12 months I've seen three major accidents involving vehicles misunderstanding the turn towards the bridge at that location. One vehicle hit a parked car, misunderstanding the Capitol Way South continuation. One careened into a house just before the turn, and a final one hit a tree head on.
Thursday, June 18 Report this
Yeti1981
Interesting article. Regardless of one's views on growth, roundabouts have demonstrated safety benefits and have become an increasingly common tool throughout the region.
One aspect of the discussion that often gets overlooked is that transportation improvements are not solely responses to new development. Projects like the Capitol Boulevard/Trosper improvements also benefit existing residents, improve safety, support local businesses, reduce emergency response delays, and help accommodate future economic activity.
The challenge for local governments is balancing infrastructure investments, housing needs, economic development, and affordability. Transportation projects carry costs, but they also create value for the communities they serve.
Thursday, June 18 Report this
Southsoundguy
Roundabouts expand the concrete wasteland, especially when combined with zoning and building codes that, philosophically, are stuck in the early 20th century.
Thursday, June 18 Report this
The_Armed_Gardener
Why roundabouts are good. #1 police and judges don't focus on public safety, just enforcement of feelings and trends. #2 roundabouts are complicated for mentally preoccupied/mentally deficient drivers. It gives them a mental check on how retarded they are. #3 It lowers the impact of the retarded drivers on pedestrians/junkies, other retards, and people on their phones, etc. #4 THERE IS LESS WAIT THAN A TRAFFIC LIGHT, because getting home to your Facebook post responses and your dog, cats, stash, and newly created support system matters more than reality.
Friday, June 19 Report this