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Tuesday, July 28, 2009

Circular Logic

Tonight I did a very friendly thing and helped a buddy of mine move from Columbia to Gaithersburg. It's a cumbersome route to drive, but I was determined to avoid the rush hour freeways and see what little remained of the northeastern Montgomery County rural areas on the back roads. It is not actually a bad route, if not for the constant stop-and-go through Ashton, Olney, and Gaithersburg.

Woodfield Road, which is currently being widened, at Fieldcrest Road. This intersection could have been a roundabout, but instead the county has decided to induce more demand along this route. (Photo by thisisbossi)

Most of my route (MD-108 to Fieldcrest Road/ to Woodfield Road/MD-124) was two lanes roads, but these two lane roads would mushroom to as many as seven lanes at major intersections. This phenomenon is obviously to prevent long backups at these traffic lights. And in such suburbanized areas, people are driving to get anywhere, hence the percieved need to prevent such backups.

But I noticed that, even during the end of rush hour, I would sit at a traffic light for as many as 90 seconds without a single other car at the intersection in any direction. This made me think of something I read via GreaterGreaterWashington's Dinner Links a few days back; roundabouts as a traffic solution.

As time goes by, intersections grow wider, adding capacity to these suburban intersections. the stretches between the intersections are often are widened shortly after. I noticed this happening on Woodfield Road during my drive. Once this happens, the overall capacity of the road is increased, which induces demand, ultimately contributing to more traffic.

Perhaps before we widen roads in suburban Maryland, we ought to try putting roundabouts in at these intersections. They would improve the flow of traffic without adding more capacity and inducing more demand. Overtime, this would save billions in construction costs. It would reduce the maximum speeds of the cars driving the routes, making the roads safer. But it would not add more time to the trip. During off-peak hours, it might even speed up trips. Other safety bonuses: roundabouts decrease the number of points for a collision to take place by 75%, and also eliminate people speeding up to make a green light. It would save gas, as the article in the above link mentions, accelerating from a dead stop is the least efficient thing an internal combustion engine can do. This would decrease the need for that greatly. And if Gaithersburg ever decides to return to its once-progressive planning style, it would facilitate pedestrians more safely and efficiently.

The fact of the matter is that this could serve as a solution at suburban intersections anywhere, and even many urban intersections. Once the capacity is added and the demand is induced, however, it would be a lot tougher to implement. So why haven't we started doing this on our two- and four-lane roads? Why perpetuate a cycle of increased traffic when we could more easily perpetuate a cycle of efficient traffic flow on our suburban routes?


Carmen said...

That is a really interesting thought. What are some good examples of these in more "rural suburban" areas.

I can think of Cape Cod for one - they have these everywhere!

I bet they would work in Lancaster, PA as well...

Bossi said...

The State includes consideration for roundabouts at all intersections. However, during peak hours, a number of locations would fail -- either high volumes overall or specifically high left-turn volumes. MD 108, in particular, has quite a number of locations which wouldn't pan out.

If you're on the mainline and are getting stopped at signals despite there being no traffic on the cross-street, you may wish to call the Montgomery County Dept. of Transportation at 240.777.6000 to ask that they verify the detection is working properly. The MCDOT maintains all such infrastructure in the County, even along State roads.

...And being a LanCo native: I second Carmen's comment!