Friday, July 20, 2012

Roundabout reservations

Many readers and folks beyond know that I've become one of many side advocates of Friends for a Better Boulevard, and I support almost everything that has been said by Bob Kemper and others that have gotten very entrenched in that fight for a better boulevard for OKC. That said, I concede that I was erroneously espousing the term traffic circle when what has really been envisioned is a roundabout, and there is apparently a very major difference between the two.

To paraphrase, a roundabout is a perfect circle where entering traffic yields to everything else and exits right to leave the circle. A roundabout is more of an orbital intersection, less of a perfect circle usually, where the lanes flow out and staying in the roundabout requires left turns. Roundabouts can efficiently handle a large volume of traffic but can not safely accommodate pedestrians, whereas traffic circles are the opposite.

Here is a chart created by WashU and distributed by Friends for a Better Boulevard (click to enlarge):
























This looks fine and dandy, but I think it raises questions as to which of these we really want. I agree that this intersection will have to handle large volumes of traffic, but I am uncomfortable with it doing that unless major design concessions are made to promote walkability in and out of the circle as well. Why would we put an arch and a park in the middle of this, just to improve the view that motorists have, esp if people can't get to it?? I'm wondering if there is a way to engineer a hybrid roundabout and traffic circle.

Let me make one thing clear before I even open up this can of worms, and before anyone accuses me of straying from the reservation: I support whatever the consensus alternative is to anything above-grade. I just also agree that this debate needs to play out. For instance, while I love the amazing renderings produced by Andrew Stewart, who has also been helping the group, the bone I have to pick there is that Western Avenue does not flow into the circle. For me, Western Avenue and its high traffic counts, high prominence, high blight factor, and huge rent gap potential for development, is one of the main reasons to do this intersection RIGHT. I want to be on the record supporting the movement in its entirety and I support whatever a public process would yield, that said, I am looking to see Western Avenue flow directly into a circular roadway that can also accommodate pedestrians. A circle of some sort that does not accommodate Western OR pedestrians is only half as sweet.

Having made my unconditional support clear, I keep going back to the name "better boulevard." To me, a better boulevard means something other than the strict and narrow purview of what is better for motorists. I am looking for what is better for pedestrians, for bicycles, for transit, for quality of life, for the environment, for economic development, and the entire city as a whole. While there is no doubt that a roundabout is far superior to those ends than an earthen ramp or anything above-grade, I would also suggest that an old-fashioned traffic circle may be even better. IF there is a way to make a traffic circle work for high traffic counts.

3 comments:

Unknown said...

The shape of the circle does not define a modern roundabout. It is the yield on entry, the deflection on entry and the design speed of 20 mph. Modern roundabouts come in circle, oval, dumbell and peanut shapes.

Unknown said...

If you want to see the difference between a traffic circle, a rotary (UK roundabout) and a modern roundabout, search www.k-state.edu to see pictures. The FHWA has a video about modern roundabouts that is mostly accurate (http://www.youtube.com/watch?v=uhHzly_6lWM )

Modern roundabouts are usually not large enough to have a park in the middle and most state laws prohibit pedestrian crossings of the circular roadway.

NR said...

My point is just that whatever form of roadway is selected needs to be able to accommodate pedestrians in the center of it, especially if we're to include a Veteran's memorial there.