Friday, April 11, 2008

More Lanes, More Parking

They're planning to add a 3rd exit lane to the Fields Ertel exit.

The solution is not more lanes. The solution is optimizing traffic lights.

Cincinnati tends to use traffic lights like airlocks. Light A turns red, and traffic backs up all the way to Light B and beyond. Light B turns red, and Light A turns green, releasing the traffic in the airlock. It stays green for awhile even though the airlock is empty. When Light B turns green, and the traffic behind it starts moving, Light A turns red again.

Examples of airlocks can be found all around Fields Ertel and Mason Montgomery area. The whole area is just one gigantic, grid-locked parking lot. There's simply nowhere for cars coming off of I-71 to go when they reach the end of the exit ramp. Adding more parking on the exit ramp isn't going to solve the problem.

The interchange of Reed Hartman and I-275 is another perfect example of an airlock system. When I lived up on Fields Ertel, I used to take Reed Hartman to get to work everyday. And every morning, I would wait through 8-10 light cycles to cross over I-275. (I had plenty of time to count them, as I sat there for 20 minutes drinking my coffee.) They attempted to "fix" that interchange by doubling the number of lanes, at a cost that would probably boggle my mind if I knew what it was. Reed Hartman now has EIGHT lanes, but traffic still doesn't flow across I-275-- There are just twice as many cars parked in the airlock now.

Traffic planners in this city seem convinced that the purpose of traffic lights is to stop traffic, but really, the purpose should be to optimize the flow of traffic. When I was working on my thesis up in Cleveland, I had to drive across town to Metro Hospital every day. I could drive on Carnegie Avenue all the way from I-90 to Cedar Hill (a distance of over 3 miles through a densely urban area) at nearly 50 mph without stopping for a single light. The lights had been optimized to move traffic out of downtown as quickly as possible during the 4:30 - 6pm rush hour, and I can tell you from first-hand experience that it's simply amazing to see what happens when lights are used to keep traffic flowing.

Thousands of cars sit idling at lights all over Cincinnati right now. Starting and stopping burns much more fuel than keeping cars moving. Think of how much gasoline usage and auto emissions could be reduced if traffic planners just eliminated airlocks and optimized lights to keep traffic flowing.

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