Induced demand sounds good in theory but leaves truckers in a jam

November 10, 2021

John Bendel


The Rocky Mountain Institute and some other environmental groups believe we should not expand highways to ease congestion. To prove it, they’ve launched the State Highway Induced Frequency of Travel Calculator – SHIFT, for short. Land Line Media’s Tyson Fisher wrote about it recently.

It’s all about something called “induced demand.”

The economic concept of induced demand applied to traffic says that highway improvements to ease congestion simply attract more traffic. Within five to 10 years, the congestion is back. The calculator shows how many million metric tons of carbon dioxide equivalent will result from any given highway improvement. The calculator is designed to discourage officials and planners from adding highway lanes to ease congestion. There are better ways of “connecting people to jobs and opportunity,” said a press release from the RMI.

Jobs and opportunity do not apply to trucks that can’t navigate bike trails, ride on buses, or walk. But that is apparently beside the point. Though we share the same roads, we’re talking exclusively about cars.

I’m sure widened highways do attract more traffic. But that new traffic doesn’t suddenly materialize from nowhere.

Those are real people in those cars as well as trucks who have real reasons for driving from point A to point B. Mom and Dad don’t one day say, “Hey kids, let’s take a ride on that nice new lane on I-301.” And if they do, they certainly don’t do it every day at 7 a.m. for the morning commute (unless they need more people for the high-occupancy vehicle lane, another bad-for-trucks idea).

Traffic comes from new populations and other routes, maybe local streets, where any reduction in traffic is a safety benefit, if nothing else. Like water, traffic takes the path of least resistance. If congestion reappears on a newly expanded highway, it means fewer cars and less congestion somewhere else.

In an online FAQ document, RMI points to other, long-term alternatives to highway expansion. One is what they call Smart Growth, “an overall approach to development that encourages a mix of building types and uses, diverse housing and transportation options” among other things. In essence, the idea is to concentrate homes, shopping, and jobs within smaller areas to reduce if not eliminate the need for cars.

A fine idea, but one that wouldn’t have a significant effect on overall traffic any time soon unless we bulldozed the existing suburbs. That would not be a popular option.

Then there is public transportation. But buses and trains are point-A-to-point-B services that don’t serve our suburbs well. Park-and-ride lots are limited by the cost of real estate.

Finally, we have “road and parking pricing.” Here we impose higher tolls at peak travel times. Maybe we impose fees to enter certain parts of a city where we raise parking prices. It may or may not reduce the number of cars downtown. In limited circumstances it can force some drivers onto public transportation, but its effect on overall traffic is another matter.

Of course, they charge trucks as well as cars – as though trucks have any options.

It also fleeces anyone who happens to hit an area at the wrong time of day. But hey, it’s more revenue for the state, county or municipality collecting the fees.

I’m guessing planners realize that trucks have no real options. They’re simply stuck in traffic jams. Maybe there’s nothing for our industry to do but watch while planners come up with ever more plans to avoid the highway improvements that have to be done – like it or not.

Whatever happens with passenger transportation, the numbers of trucks will grow with the population. Period. That’s one reason the induced demand idea – an economic concept – is not well applied to vehicular traffic with constraints and imperatives that don’t exist in general markets. It’s just a lumpy fit.

I don’t question the accuracy of the SHIFT calculator’s results. I just think we need another calculator, one that shows the environmental and economic costs if we don’t expand highways to relieve congestion. How many millions of metric tons of pollutants are released when congestion is not eased, when cars and trucks are diverted onto local roads and the same traffic jams remain unmitigated day after smoggy day? LL


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John Bendel is Land Line’s contributing editor-at-large. A former trucker, former editor at National Lampoon and two trucking magazines, John is an author, photographer, and freelancer. His work has appeared in the New York Times, The Washington Post, and many U.S. newspapers.