Pedestrians cross thru traffic on "K Street" as traffic is at a stand-still on the streets of Washington, DC with downtown rush hour gridlock on January 26, 2011, as a powerful snowstorm pounds the city. Commuters had drives home that were 6-8 hours long rather than 60 minutes to the suburbs and several hundred thousand greater Washington, DC, Virginia, and Maryland, residents lost electrical power. Hundreds of flights were canceled and schools closed because of a snowstorm that was expected to dump up to 12 inches (30 centimeters) of snow on US east coast cities. AFP PHOTO / Paul J. Richards (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images)
In one of the interviews with Jane Jacobs after the publication of Nature of Economies, I remember an exchange with regard to road capacity. When asked about why isn't there enough road capacity, she replied:
"You're asking the wrong question. The right question is 'why are there so many cars?'"
I mention this because the main question with regard to the snowstorm-commuting debacle on Wednesday becomes one of road capacity
and overburdening the system.
It's not just about road capacity generally, but of road capacity in suboptimal conditions, and in a system with a number of chokepoints -- for example there are only 5 bridges connecting DC and Virginia (+ two subway tunnels) and that means that all the traffic has to get through those 5 bridges.
The capacity of one mile of freeway lane in optimal conditions is 2,200 cars/hour. Suburban arterials probably have a capacity of about 1,300 cars maximum (the figure is dependent on the number of lanes and the number of entry points per mile and of course the speed limit and the conditions). City streets maybe 800/cars/hour/lane. And remember that with short blocks (300-400 feet in length) the queuing capacity/lane is not large.
The fact is that in an auto-dependent mobility paradigm, when you have hundreds of thousands of drivers leaving work at the same time, having to drive more slowly in suboptimal conditions, with car and other breakdowns reducing the number of open lanes, and all converging on a relatively small number of entry/exit points simultaneously, you have the recipe for disaster--if you are automobile dependent.
The thing is that this is nothing new. I have written before about similar events over the years, and my experience on my bike cruising by blocks and blocks of stalled traffic (such as that backed up for entry onto I-395 at Massachusetts Avenue NW).
The solution of course is to prioritize transit (even so there is little slack capacity in the system to add service), including snow removal on bus routes, but also to create an early release schedule that is based on shifts, whereby certain agencies are assigned leave times, with the idea that there is a gradual release of workers so that the system is not completely overburdened at the outset.
The thing is that isn't how the federal government has done it in the past. Directors of the Office of Personnel Management are new with each administration and lack institutional memory.
Plus it is politically difficult now to make decisions about letting people leave work early because of the rampant bashing of federal workers and the federal government.
It's too difficult to try to explain to people that the problem really has to do with the mobility paradigm, mobility capacity, the onset of the worst of the storm during "rush hour" and a flawed process for early release which inadequately takes these factors into consideration.
If you work within 5-10 miles of where you live and you have good transit access, while it might take a little longer to get home, you should be okay. If you live farther away, or in locations where your mobility is car-dependent, any substantive breakdown in the capacity and throughput of the road system will lead to catastrophic delays.
When the system is broken, it's easy to blame public officials for their failures, but the fundamentals of the problem are much deeper and less facile that editorial writers seem to understand.
For example, to add capacity, the editorial suggests opening unused lanes in the other direction (southbound 16th St. for example) without recognizing the legal requirements for doing this safely are considerable--barriers, roadblocks, police-traffic enforcement personnel at major intersections, etc.--and would be difficult to pull off on a moment's notice even in optimal conditions of temperature, weather, time of day, and visibility.
Instead, I call that a prescription for more accidents and more problems, not fewer...
Road Congestion as a Policy Driver in spite of the system complexity. MIT class diagram.
Labels: transportation demand management