It's not every day that you write a letter to a respected policy blogger and have him openly admit that the letter changed his viewpoint radically. I now direct you to my letter featured on Matthew Yglesias' digs. The first thing you will notice is that my letter in no way caused a re-think on Yglesias' part, nor did it even contain a point, per se.
The Dallas Morning News reported on a construction project about to be undertaken by a Spanish firm along the 635 corridor in North Dallas--my stomping grounds. This five year operation will dig beneath the current highway to build new toll lanes. No additional free lanes will be built, only toll lanes. Most importantly, the price of the toll will fluctuate based on current traffic conditions: during rush-hour (when 635 is unbearable), the toll might be several dollars.
Unfortunately, I was in such a rush to get the email off to Yglesias that he (understandably) mistook my question about whether or not such an operation is likely to "work" as a question only about the likelihood of the toll lanes to decrease congestion and not about the likelihood of the presence of the toll lanes to decrease congestion on the free lanes.
In Tom Vanderbilt's "Traffic: Why We Drive the Way We Do", the author states forcefully that, based on all available studies, building more lanes does not decrease congestion. Rather, more lanes simply invite more traffic. This happens because humans are unusually adept at planning for, negotiating, and avoiding traffic. Therefore, when new lanes appear, it won't be long before commuters recognize the additional lanes and adjust their travel patterns accordingly (i.e. instead of taking I-90 to 35 to work, they will take 635 to 35 thanks to the additional roadway). At first traffic will be noticeably smoother, but we shouldn't expect this to last long as additional cars (containing humans making rational decisions) will fill up the new lanes recreating the congestion the additional lanes were intended to fix.
The question Yglesias took me to be asking concerned the toll lanes. His response: "Naturally, everyone wants to take the free road. But as 'everyone' tries to crowd onto it traffic moves slowly and some people will want to exchange money for time by taking the toll road. And at any given time of day, there’s got to be some price at which the tolled road will be uncongested." So, yes, the toll roads will "work."
But the question I am really concerned with is the free lanes that the average commuter uses on a daily basis. My initial thought was that the more people that opt for the toll lanes, the more space there will be in the free lanes for the traffic that does not want to pay tolls. But one of the commenters to Yglesias' post says this is incorrect, and instead uses the logic of Vanderbilt's book to argue that the free lanes may experience less congestion for a short period of time, but before long, more traffic will come to fill the openings left by those cars willing to pay the toll.
A couple commenters disagree with the basic idea (c/o Vanderbilt) that it's impossible to build enough roadway to counteract the increased amount of new traffic. They argue that people don't drive around aimlessly, so there will not always be a constant stream of new traffic to occupy all available lanes (in other words, drivers will not notice available roadway and drive on it just because they can--remember, drivers are surprisingly strategic).
Another interesting point presented by a commenter is that the more roadway constructed, the less available space for city-living. I would be inclined to agree with this if not for the extreme driving culture that we see in Dallas/Ft. Worth. The infrastructure in Dallas is phenomenal; from the High-Five to the Mix-Master to the DFW-Connecter, our roads are--while certainly headache inducing--beautiful in their utility and vision. The Ancient Romans would, once they understood how we managed to survive without slave labor, marvel at our infrastructure accomplishments. Thus, in Dallas, I believe, road construction could continue on indefinitely (through double-deckers, under-grounders, etc.) without any loss to the spirit that is Dallas.
Whether or not all of this is a good thing for the environment and human prosperity is a different question entirely. Suffice it to say, I am--as I always am--intrigued by the lastest attempt to efficiently move capital from the suburbs and exurbs into the heart of the Metroplex. Forget the impending apocalypse, the Dallas Megalopolis is stunning.