Debunking the Induced-Demand Myth

“Building bigger roads actually makes traffic worse,” asserts Wired magazine. “The reason you’re stuck in traffic isn’t all these jerks around you who don’t know how to drive,” says writer Adam Mann; “it’s just the road that you’re all driving on.” If only we had fewer roads, he implies, we would have less congestion. This “roads-induce-demand” claim is as wrong as Wired’s previous claim that Tennessee fiscal conservatives were increasing Nashville congestion by banning bus-rapid transit, when actually they were preventing congestion by banning the conversion of general lanes to dedicated bus lanes.

In support of the induced-demand claim, Mann cites research by economists Matthew Turner of the University of Toronto and Gilles Duranton of the University of Pennsylvania. “We found that there’s this perfect one-to-one relationship,” Mann quotes Turner as saying. Mann describes this relationship as, “If a city had increased its road capacity by 10 percent between 1980 and 1990, then the amount of driving in that city went up by 10 percent. If the amount of roads in the same city then went up by 11 percent between 1990 and 2000, the total number of miles driven also went up by 11 percent. It’s like the two figures were moving in perfect lockstep, changing at the same exact rate.” If this were true, then building more roads doesn’t make traffic worse, as the Wired headline claims; it just won’t make it any better.

However, this is simply not true. Nor is it what Duranton & Turner’s paper actually said. The paper compared daily kilometers of interstate highway driving with lane kilometers of interstates in the urbanized portions of 228 metropolitan areas. In the average metropolitan area, it found that between 1983 and 1993 lane miles grew by 32 percent while driving grew by 77 percent. Between 1993 and 2003, lane miles grew by 18 percent, and driving grew by 46 percent.

That’s hardly a “perfect one-to-one relationship.”

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Voting Themselves Bigger Budgets

An implicit principle in a democracy is that the officials who decide how your taxes are spent represent you, the taxpayers, and not the bureaucracies that receive your taxes. But Congress violated this principle when it wrote MAP-21, the 2012 transportation law. As detailed in a proposed rule earlier this month, the law gives transit agencies in major urban areas a vote on how much of each region’s transportation dollars are spent on transit.

State legislatures are made up of people elected by various voting districts, not representatives selected by the state departments of transportation, justice, welfare, fish & wildlife, parks, and other bureaucracies. Similarly, city councils are made up of people elected by the voters in that city, not by representatives selected by the various water, transportation, fire, and other bureaus.

In 1962, Congress mandated that urban areas of 50,000 people or more create metropolitan planning organizations (MPOs) that would decide how to spend federal transportation and housing funds. At that time, it recognized this principle, specifying that the governing board of each MPO consist of elected officials from the various cities and counties in that urban area. While this was one step removed from the voters, it at least insured that the voters had an indirect say over how their money is spent.

However, MAP-21, the 2012 law reauthorizing federal transportation funding (including funding for MPOs), departed from this principle by requiring that transit agencies in all urban areas with 200,000 or more people be given representation on the MPO boards. In other words, the bureaucrats themselves will get to vote on their own budgets.

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Cut Saturday Mail to Fund Highways?

The Highway Trust Fund will be out of money in a few months, mainly because Congress insists on spending more than it takes in. To avert this supposed crisis, Republican leaders are proposing to cut Saturday deliveries of mail and use the savings to replenish the trust fund.

There’s actually a tiny grain of Constitutional sense behind this proposal. The original legal justification for federal involvement in highways, back when members of Congress actually cared about such things, was that the Constitution authorizes Congress “to establish Post Offices and post Roads.” If the “post roads” aren’t paying for themselves, then who better to pay for them than the post offices?

In this sense, the Republican proposal is slightly more rational than President Obama’s proposal to use the increased revenues from a corporate income tax reform that will eliminate loopholes but reduce corporate tax rates. The administration predicts reducing rates will reduce corporate tax obligations in the long run but closing loopholes will increase revenues in the short run (interesting how Obama is promising corporations lower taxes after he is out of office in exchange for higher taxes when he is still in office). Obama wants to use some of those increased revenues to supplement the Highway Trust Fund.

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The Low-Capacity, High-Cost Transit Scam

Mumbai opened a monorail last week, the first 12 miles of what is planned to be an 84-mile system costing a total of US$2 billion. A high-density city like Mumbai may be one of the few places in the world where rail transit makes sense. But the Mumbai monorail has a design flaw that makes it as stupid as the most idiotic rail lines in the United States (of which there are many candidates).


Not only are Mumbai’s monorail trains small, their average speed is just 20 mph. Wikimedia commons photo.

That flaw is that the trains are no more than six short cars long, and can run only every three minutes. Even at crush capacity, the system can move only 7,400 people per hour. That’s a tiny fraction of what a real high-capacity rail system can move. New York’s Eighth Avenue subway line can move 30 ten-car trains per hour, and each car has a crush capacity of 240 people, making it capable of moving 72,000 people per hour. Americans won’t accept crush-capacity conditions, but even at American levels of crowding, New York subways can move at least six times as many people per hour as the Mumbai monorail.

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