Last week, the Toronto Board of Trade suggested adding lanes to Highway 401 — either by adding upper decks or by tunnelling — in order to, as the headline read, “ease gridlock.” The price? Maybe as much as $10 billion.

The idea of taking the stretch of that highway running through Toronto, already 16 lanes across, and adding levels that zip above and below it like a real-life Hot Wheels track might have some playroom appeal (no word yet on adding a loop-de-loop). Certainly the idea of easing gridlock sound good.

But it ain’t gonna work. Adding lanes to congested highways never does for very long.

The reason it is doomed before it even gets started is even listed in the Board of Trade report, under the “drawbacks” column in a comparative table they provide for consideration.

“New highways can cause sprawl,” the report notes, before getting to the really bad news: adding lanes “may not solve congestion, as more users will be attracted to the new capacity quickly, resulting in congestion once again.”

That’s a pretty big drawback: spending roughly the equivalent of the entire city of Toronto’s annual budget on a years-long construction project that promises to ease congestion that, at the end, results in no change in congestion.

But that is what usually happens when big, thriving cities add road space.

That bullet point in the Board of Trade report is a brief paraphrase of a very famous rule of traffic. The “Fundamental Law of Road Congestion” was named by economists Gilles Duranton and Matthew A. Turner after a study of 20 years’ worth of road travel data from U.S. cities. They found that the number of cars miles travelled rises to meet the number of available miles of road. That is, the travel speed on an expanded highway reverts very quickly to its previous level. Or,, in their words, “Increased provision of interstate highways and major urban roads is unlikely to relieve congestion of these roads.”

You can picture a sink in which the drain is backed up, so the basin is getting full and might overflow. Is making the basin larger likely to help? No. It will still be backed up, just with more water. Worse still, the observation is that usually if you make the basin bigger, people will run the tap longer, feeding even more water into it, so it threatens to overflow again. Constantly.

The Board of Trade report points to two relatively smaller highway projects in Texas to estimate costs and feasibility, which prompted my old Twitter friend @madhatressTO to recall another recent highway example from Texas.

After a major reconstruction completed in 2010, the Katy Freeway near Houston became known as the widest expressway in the world. Building it out to 23 lanes took five years, at a cost of $2.8 billion. For that, it even included the kind of “super express” high-occupancy and toll lanes the Board of Trade suggests for the 401.

When the highway reopened, lawmakers were pretty proud of what they had accomplished. Before reconstruction in 2005, the trip from downtown to a place called Pin Oaks on the Katy Freeway would take about 52 minutes during rush hour. In 2011, that trip was reduced to just under 47 minutes. A five minute savings!

But by 2014, the gains had not just disappeared, but the trip was worse than ever before. The wide highway attracted more traffic, and the trip out to Pin Oaks now took 70 minutes, 27 seconds — an increase of more than 50 per cent over 2011, and a 33 per cent increase over the pre-construction travel time. The entire gain from all that money and time was not only eliminated but reversed in about three years.

This isn’t surprising. It happens all the time. In 2014, after five years and a billion dollars worth of construction, I-405 in Los Angeles was reopened, wider than ever. Within one year of reopening, traffic was moving slower than it had been before. Vox reports that studies have found the same effect in the U.K., in Japan, in Turkey. Everywhere. If you build more road space, it “generates traffic,” wrote Todd Litman in the Institute of Transportation Engineers Journal in 2001.

What can ease congestion, Duranton and Turner found, are road tolls, which the public hates. The other thing that can work is a recession, which reduces the number of commuters because people have no jobs. This is also an unpopular solution, for obvious reasons.

The Board of Trade calls its proposal “bold.” That’s one word, I guess, for a years-long infrastructure project that evidence shows is unlikely to help, and may even hurt.

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But spending billions of dollars on something like that, when there are so many other things crying out for funding, suggests some different “b” words: batty, boondoggle, BS.

Back to the drawing board.

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