11th Street bridges, part 2: Traffic effects
Part 1 looked at DDOT's ambitious, $500 million project to replace the 11th Street bridges across the Anacostia. The reconstruction will add "missing" ramps and a local bridge, but also more traffic lanes across the river. What will be its ultimate effect?
The Capitol Hill Restoration Society, which opposes the project, hired transportation consulting firm Smart Mobility to analyze the project. At first, DDOT refused to even release their traffic model, but Councilmember Wells intervened to get the data. Smart Mobility found many flaws in DDOT's original analysis. Their model predicts that this project will divert a significant amount of traffic off the Woodrow Wilson Bridge:
I colored the freeway diagram based on the map in the Smart Mobility report. Roads in red are those which should see an increase of 300 or more vehicles after the project in the afternoon peak; green roads would see a decrease. (I colored both directions of each road the same; it's possible the morning peak will differ slightly.)
DDOT's response is unconvincing:
It demonstrates that afternoon peak period traffic volumes increase on some links and decrease on other links. In general, traffic increases on I-395 through Virginia and the District of Columbia, and decreases on I-495 and I-295 through Virginia, Maryland, and the District of Columbia. Traffic on most of the local streets does not change or decreases. This is consistent with the Purpose and Need for the project, which is to "reduce the volume of freeway traffic that spills onto the neighborhood streets due to current traffic patterns". ...Moving traffic from the local streets to the freeways is a laudable goal, but the Smart Mobility report doesn't agree that all local streets will benefit. Pennsylvania Avenue, for example, will have lower traffic on the Sousa Bridge, but more traffic on both ends. That's probably because, if the Sousa Bridge becomes less congested from commuters going from the Southeast Freeway to 295, other commuters will start using the bridge.
[T]eh increase of traffic at the 11th Street Bridges is offset by a decrease in traffic on each of the other Anacostia River bridges. The net increase in daily Anacostia River bridge crossings is only 5 percent.
Even if the project did divert all the traffic off local roads, DDOT's are ignoring all other effects. Moving traffic from local streets to freeways by significantly increasing DC's freeway capacity will also generate a lot more pollution in areas where many people live close to the freeways, especially east of the river. The Bronx has one of the world's highest asthma rates not because of a lot of traffic on local streets, but because it's crisscrossed with freeways.
Finally, the 5 percent increase DDOT expects across the Anacostia River is not a trivial amount. It can make the difference between smoothly flowing traffic and stop-and-go traffic. Just a tiny increase can push a freeway over the edge and cause it to "crash" into slow-moving sludge. The other bridges' reductions offset most, but not all, of the increase in traffic. In other words, we will indeed see more traffic.
More freeway capacity in DC will also move people off of Metro and induce new trips in the long run. The Smart Mobility report claims DDOT hasn't properly modeled induced traffic; DDOT claims they did, but doesn't deny that the project will indeed induce more traffic. They only argue that the original FEIS already accounted for all the damage to DC's air quality that the project will create.
Connecting the "missing ramp" will indeed take traffic off the few blocks right around the interchanges, traffic which today has to exit and re-enter the freeway system. However, DDOT hasn't satisfactorily explained why we can't add in those connections without widening the bridge. The FEIS doesn't present a narrower bridge as an option, for example. In the quest to get traffic off local streets, we'll just end up getting more traffic on some other roads and more traffic in total. The pollution doesn't stay right over the freeway, and spending $500 million to add more traffic doesn't sound like a very smart idea.
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