Comparing roundabouts and traffic signals

The in basket: Al Shelborne of Kingston wants to know the cost comparison of traffic signals versus roundabouts , such as the one being built at the intersection of Holly Road and Seabeck Highway.

And Cindy Warwick of Seabeck spoke for what I’m sure are a number of skeptics that a roundabout is a good idea there. “Are they crazy?” she asked. “This roundabout thing isn’t going to work.”

The out basket: Cindy didn’t get a lot of comfort from me, as I have come to regard roundabouts as a major improvement in traffic control. Like yellow flashing left turn signals, they save a lot of waiting and idling, from a driver’s perspective. We’ll get to the Kitsap County’s perspective in a moment.

There is a learning curve with both, of course, and my stepdaughter, Ronda Armstrong, who lives out there, says she has seen a few drivers at the under-construction roundabout on Seabeck Highway turn left into it from Holly Road to go toward Silverdale, rather than going around to the right, as is required.

It’s hard to understand how a driver could be that unacquainted with roundabout driving with so many of them being built, so maybe those folks just decided to take advantage of the incompleteness of it all to save a second or two.

Anyway, about comparative costs. The county did a direct comparison of a roundabout and traffic signals before it built the Newberry Hill-Chico Way-Silverdale Way roundabout and found the signals to be slightly more costly. I wrote at the time that that analysis probably wouldn’t persuade a roundabout-hater, as there were a lot of variables and assumptions.

This time, they didn’t bother with such a cost comparison (sorry, Al) , and hang their hat on the greater safety and lower ongoing maintenance and operation costs.

Here’s how Tina Nelson, the county’s senior program manager puts it:

“The county conducts a traffic study for every Roads Capital Improvement Project. Typical study elements for an intersection are operation and safety. The data collected told us that traffic control was needed at the intersection to improve the flow of traffic.

Ronda steps in to put a little meat on the bones of that assertion. She says cars coming toward Holly Road from the north are in a curve and often travel at a speed that leaves those waiting to pull out from Holly Road uncertain whether they dare go in case the approaching driver doesn’t turn right onto Holly, as most of them do. If they guess wrong and pull out, a serious T-bone accident can result

Back to Tina. “Our primary improvement in the past has been to install a signal,” she said. “Now with roundabouts and their advantages, we seriously consider them as an alternate to signals. Roundabouts don’t have the maintenance and operations requirements that signals have and they nearly eliminate severe collisions.

“On the flip side they typically require more land space than a signal does.

“The county policy is that: “When an intersection meets all-way stop and/or signal (criteria), roundabouts should be considered as an alternative. Based on the policy, a roundabout ended up becoming the recommended alternative.

“The traffic study specifically determined that: a roundabout would provide a better flow (operation) of the intersection than a signal and channelization, and that it would offer greater reduction in the frequency of injury crashes, and particularly in severity of crashes,” she said.


7 thoughts on “Comparing roundabouts and traffic signals

  1. Comparing the costs between a roundabout and a signal at Seabeck Hwy & Holly is a no brainer.
    A signal would require a dedicated left turn to Holly, add to that the cost of signals and maintenance.
    The roundabout wins everytime, once the drivers are used to the the protocols of the roundy, it will settle down.

  2. Obvious choice, inexpensive rural land, relatively level topog, no major environmental issues or permits (shorelines), all compared to Newberry Chico. Seems like after the unrelated utility improvements were done, went in about 1/2 the time of Newberry. No cost comparison needed. Will be interesting to see the input after more complex multiple lane roundabouts go in such as Treemont.

  3. First cost is the wrong way to compare projects. It would be like buying a car without know the fuel economy or safety of the thing, just its price to buy.
    Present Value Life Cycle Cost Analysis (LCCA) is the best way to compare two or more choices. When comparing modern roundabouts to signals for a 20-year life cycle (the standard period), modern roundabouts usually cost less. Costs to compare include: first cost (design/land/construction), operation and maintenance (electricity, re-striping, upgrades, etc.), crash reduction (what’s your/your family’s safety worth?), daily delay (what’s your time worth?), daily fuel consumption (spend much on gas?), point source pollution (generated by stopped vehicles = health cost), area insurance rates (this costs more where it is less safe to drive). Each of these things, and others, can be estimated for any two choices and everyone near or using the project area will pay some portion of all of these costs. More info:

  4. I am reserving judgement on the roundabout at Holly until it is completed. We have a business on Holly Rd. that has been significantly impacted by construction because we can’t bring semi-trucks in through the roundabout while it is being built. The main issue is that the curbs being pored – which are SUPPOSED to be run-ups for longer wheel-based vehicles – are currently too tall to get a truck and trailer through there. I am concerned about how narrow the approaches from Seabeck Hwy are into the roundabout at this point – in looking at them I worry that there won’t be sufficient room on the apron for run-over for the larger vehicles. Right now we have to go up Newberry Hill Rd. and around via Seabeck. It is a major hassle, adding time to trips AND Newberry is much steeper than Seabeck Hwy which is challenging.

  5. The roundabout on seabeck/ holly has been built really fast- they were predicting 20 min delays but I have yet to wait more than 2 minutes. Other than being a little dusty in the evening (they keep it watered down during the day) I have no complaints. I really would like to see what they are going to put in the center of it. It would be nice to have something like Silverdale has – maybe Gateway to Seabeck/ Holly? We do have lots of public lakes, parks and recreation in that area..

    1. I’ve sat there for 20 minutes and know others who have also waited that long. You’ve just been lucky! I wish it would have stayed the same since I just use Seabeck Highway and never turn onto Holly. I might like it better than a stoplight though’ time will tell.

  6. You know the biggest issues with a round-a-bout is the fact that people just cant figure them out. They drive up to one and most of the time come to a complete stop when there are not even any cars in one and despite the fact that most people use their turn signals the drivers will still wait for the circle to be completely empty. And if there a a few drivers in a row that do that, it is worse than those people who cant merge on highway 3 from auto center way going towards gorst. And another thing that is worse than those who wait to go is those who either get lost in the round a bout or stop in one. And then they gripe about how those things are the worse inventions despite the fact we are one of the last countries to use one. And even those drivers that dont use their turn signals, if you can get off your cell phone and read the driver that is going through the circle you can actually tell what their intention is without them using their turn signal. Example would be the Port Townsend round a bouts. There are two back to back and very seldom have I ever been stopped for more than a couple seconds and it merges pretty quick and can go at a swift speed. You can always tell those who are not from there because they are the ones who stop and wait.

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