* Adding roundabouts requires more land, which is in tight supply in a built-up city like Seattle. I don't think shaving the corners off of buildings is going to go over very well.
* As I've noted, the buildup of the cameras is very recent. The traffic light data you cited is over a year old. They're creeping into the side streets now.
* Nobody needs a study to see the obvious improvements possible in cases I cited.
* Given the desire of the government to install cameras everywhere on the roads, the cost of them is going to be there with or without roundabouts.
* Far friendlier to pedestrians? How is that possible when cars don't stop? I've crossed roundabouts in England as a pedestrian. It involves pushing a button and a traffic light turns red so you can cross. I.e. the traffic lights are still there!
* In Romania the roundabouts also had traffic lights for the pedestrians, as well as pedestrian tunnels under the intersection. That can't be inexpensive.
* I can see a roundabout as cost effective in a rural area where land is cheap and there are few pedestrians. In a builtup city, not so much, as they'd be massive and expensive construction projects. A $40,000 box can be installed instead with no disruption and immediate improvements. Sounds like a winner to me.
All modern roundabouts have median islands separating incoming and outgoing auto traffic. Pedestrians don't have to find a gap in two directions of traffic, just one. This is safer for pedestrians, especially for younger or older ones, because they only have to concentrate on one direction of traffic at a time. This is what is meant by two-phase. Cross the first half, pause if you need to, then cross the second half. On multi-lane crossings pedestrian beacons or signals are often added if the auto (or pedestrian) traffic is too numerous. The signals can also be two phase, requiring the pedestrian to push a second button when they get to the median. The median can also have a Z path to reorient the pedestrian to view oncoming traffic. Also, the signals usually rest in off, so they are only activated if a pedestrian needs the help crossing. This way only motorists that need to stop are delayed.No. Look again. The quoted text says "$1.7 million to design and build the roundabouts". Plural. That was three roundabouts, not one, on "51st Ave S, Renton Ave S and S Roxbury ST". And some of the objections you just now raised have been addressed in links I gave earlier, including examples of SDOT proposals for roundabouts in urban Seattle.
I give up. You have decided on your answer and no real-world information will change your personal beliefs. You win.
I've been in countries that are comfortable with roundabouts. They also still have traffic lights everywhere. Something is missing in your analysis that explains this choice.
Modern roundabouts are the safest form of intersection in the world (much more so than comparable signals). Visit http://tinyurl.com/iihsRAB for modern roundabout FAQs and safety facts. Modern roundabouts, and the pedestrian refuge islands approaching them, are two of nine proven safety measures identified by the FHWA, http://tinyurl.com/7qvsaem
The FHWA has a video about modern roundabouts on Youtube, or check out the IIHS video (iihs dot org).
First cost is the wrong way to compare projects. It would be like buying a car without knowing 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.
Of them, 85 are "FULL", 271 are "PRE", and the remaining 721 are "SEMI". Based on http://ops.fhwa.dot.gov/publications/fhwahop08024/chapter5.h... these appear to mean respectively "Fully-Actuated", "Pre-timed", and "Semi-Actuated", so 271 or 25% of your cities traffic lights are on a timer and don't have vehicle detectors.
Your original example was of an intersection with "cameras mounted pointing all 4 ways", making it fully-actuated. There are only 85 of those signals in Seattle, or 8% of the signals.
To be fair to you, you said "on an arterial". However, your definition of "arterial" appears to be different than Seattle's, which subcategorizes them as 'Principal Arterials', 'Minor Arterials', 'Collector Arterials'. See http://www.seattle.gov/transportation/streetclassmaps.htm . More specifically, the map at http://www.seattle.gov/transportation/streetclassmaps/planwe... shows more than 85 intersections of an arterial with an arterial, so the pidgeonhole principal say it shouldn't be hard to find an intersection that isn't fully actuated.
To be fair to me, this is completely besides the point. There are many solutions to your original problem of being stuck at a light. One is to add another layer of technology (smarter signals). Another is to switch to a different type of technology (roundabouts). All you've been doing is cherry picking your observations to justify your initial beliefs. I further believe is because you, like many other programmers, are philosophically inclined towards complex, centralized control systems, because that's what we understand and work with all day.
But the observational evidence is that roundabouts are better than signals for many situations. Please stop ignoring the evidence because your mind is set on the first solution you came up with while your were stuck at that traffic light!
For examples drawn from Seattle, from these meeting notes in 2006 at http://www.seattle.gov/transportation/docs/setscctnov06%20mt... :
> The City Council did not vote to eliminate the roundabout proposed at 51st Ave S, Renton Ave S and S Roxbury ST from the Transportation Capital Improvement Program (CIP). SDOT has secured a grant for $1.7 million to design and build the roundabouts; unfortunately, based upon preliminary design and cost estimate, additional funding is necessary. If built, it would be the first roundabout in Seattle. The project was identified in the Rainier Beach Neighborhood Plan as the most problematic intersection in SE for all modes. The roundabout could be a very cost effective solution as unlike a traffic signal, it will have minimal on-going operating and maintenance costs. Environmentally, it's better than a traffic signal because vehicles would not be idling at the light. It is also far friendlier to pedestrians, which would have the right away and not have to find the pedestrian push buttons. CCT members reiterated that the area is routinely congested and difficult to negotiate.
and from http://www.seattle.gov/transportation/docs/nctipf_chapter%20...
> Modern roundabouts can provide safe and cost-effective traffic control at some intersections. A roundabout separates through and turning traffic into designated lanes with “splitter islands” to minimize traffic weaving. Well-designed and appropriately placed roundabouts also provide safer pe destrian crossings and can accommodate large turning radii required by trucks and emergency vehicles. Today’s roundabouts do not function like the large, high-speed traffic circles found in Washington, D.C., (Dupont Circle) and Paris (Arc de Triomphe). These large traffic circles have high crash rates, largely due to high volumes, high speeds, and a considerable amount of weaving between entries and exits. Roundabouts are not the small circles used primarily for neighborhood speed control. Studies of modern roundabouts show a reduction in serious crashes, as well as reduced delay and queue length compared to other forms of traffic control, such as four-way stops and traffic signals. However, engineering analysis will not always support a roundabout over a traffic signal or other traffic control measure. Consideration must be given to traffic volumes, capacity requirements, available right of way, and cost.
There's a newspaper article from 2002 which concerns a successful roundabout in Snohomish County, at http://community.seattletimes.nwsource.com/archive/?date=200... . A round-about replaced a stop sign, and reduced the number of accidents. While it cost $310,000 and "traffic signals at that location would cost only $200,000, the roundabout requires no mechanical maintenance or electricity, making long-term costs comparable, he said. Meanwhile, traffic flows much more smoothly without a signal or stop signs."
The article also says "DOT built its first state-highway roundabout in 1998 in Port Orchard, where a triangular intersection on Highway 160 had produced 39 crashes in three years. In the first 18 months after the roundabout opened, only two accidents occurred."
Continuing from the article, "National studies show that communities usually oppose the idea at first, DOT engineer Brian Walsh said. "Our experiences here in Washington have mirrored that; we have had a lot of people not very happy about the idea of roundabouts, but after they are constructed, those fears mostly go away."
which is why when SDOT brings it up over the years, there's pushback, like:
> The roundabout concept has generally received positive or neutral comments, but there is skepticism about the feasibility of building it and also some concern about the amount of land that would be required to build it, as well as the adjustment needed for motorists to learn how to drive this type of facility. - http://www.seattle.gov/dpd/cs/groups/pan/@pan/documents/web_...
I can accept an argument that people in Seattle won't use roundabouts because no one there has the political will to push for what is, really, a safer system. But your arguments so far haven't been anything better than "trust me, I know what I'm talking about". ... Which is exactly how the current system of "smart" (ie, actuated) but dangerous traffic signals were sold to us 20 years ago.