Sandeep Baliga writes:
[In a recent study, Gilles Duranton and Matthew Turner write:]
For interstate highways in metropolitan areas we [Duranton and Turner] ﬁnd that VKT (vehicle kilometers traveled) increases one for one with interstate highways, conﬁrming the fundamental law of highway congestion.’
Provision of public transit also simply leads to the people taking public transport being replaced by drivers on the road. Therefore:
These ﬁndings suggest that both road capacity expansions and extensions to public transit are not appropriate policies with which to combat trafﬁc congestion. This leaves congestion pricing as the main candidate tool to curb trafﬁc congestion.
To which I reply: Sure, if your goal is to curb traffic congestion. But what sort of goal is that? Thinking like a microeconomist, my policy goal is to increase people’s utility. Sure, traffic congestion is annoying, but there must be some advantages to driving on that crowded road or people wouldn’t be doing it, right? (Just to be clear: I’m serious here. This is not intended to be some sort of parody of economic reasoning. I do believe that people venture out in traffic for a reason.)
Let me put it another way. Suppose that (a) Los Angeles could immediately double its existing road system, at zero cost in dollars, effort, open space, pollution, etc., and (b) if that were done, there would be exactly twice as many cars on the road at the same exact level of congestion. If this (inherently impossible) scenario came to pass, this would be a good thing, no? Twice as many people would be able to get what they want, which is to be out on the roads.
Or, here’s another one. Suppose NYC could immediately and costlessly double the frequency of its subway trains, and suppose this would (i) draw lots of people out of their cars into the subway and (ii) draw out new drivers, so the existing roads would be as crowded as possible. If the goal is to curb traffic congestion, we’ve gotten nowhere, but if the goal is to improve quality of life, we’re in great shape. I ride the subway (sometimes). If there were twice as many trains, I wouldn’t have to wait as long for a train. I also ride on the roads. The traffic congestion doesn’t bother me so much, I can still get around.
If you don’t like the NYC subway example, pick your favorite alternative, for example consider a suburban bus line that changes its frequency from once per hour to once per 10 minutes. Once per 10 minutes is great for bus riders—even if it does nothing to alleviate congestion, you don’t have to wait that extra 50 minutes at the bus stop.
My point here is not that we should be necessarily be expanding highways and transit systems: there’s a cost to subsidizing transportation, a cost in pollution and an opportunity cost because the money and resources are not spent elsewhere (maybe not such a cost right now with 9% unemployment but it’s an issue at other times). Nor am I knocking congestion pricing, an idea that seems to make a lot of sense, whether or not roads and transit are increased. My key point is that, yes, traffic congestion is annoying, but I don’t think it makes sense for “curbing traffic congestion” to be a primary policy goal. A policy that leaves traffic congestion unchanged can still help out lots of people, inside and outside of cars.
Why am I blogging this?
I’m not a transportation expert. But I think the above discussion illustrates a general principle in decision analysis, which is that it is important to consider carefully what your goals are. In the above example, traffic congestion is a problem, but I think it’s a mistake to set the reduction of congestion as a goal in itself, or to dismiss various actions because they don’t provide progress toward that particular goal.