Let's Talk About 'Induced Distance' Instead of 'Induced Demand'

Traffic management consultancy Inrix released its 2022 Global Traffic Scorecard and it's making headlines around the world. The Washington Post published "At 155 hours, Chicago congestion at No. 1 as traffic grows nationwide," while the Toronto Star ran with the headline, "Toronto ranks one of the worst worldwide for traffic congestion, report finds." Commenters in the Star complained that it's all the fault of the bike lobby: "We need to build more roads but instead the city is going in the opposite direction." Unlike Treehugger, the articles are illustrated with photos of congested highways.

Inrix wrote: "For the second straight year, London again tops the Global Traffic Scorecard as the most congested city in the world. The average London driver lost 156 hours due to congestion in 2022, but Chicago is a close second, as drivers there saw a drastic return to pre-COVID congestion levels by spending an extra 155 hours sitting in traffic. Paris rounds out the top 3 in 2022 with 138 hours lost."

Its methodology is based on comparing "free-flow data" with travel times during peak periods. "In other words, it is the difference between driving during commute hours versus driving at night with little traffic."

The crux of the issue is that last sentence—there is not a thriving city in the world where the road system is free-flowing at peak times, where it is like driving at night. It is probably impossible to achieve unless you live in Buffalo or another city that lost half its population. Congestion is a feature, not a bug, in many ways the sign of a successful, growing city.

According to Planopedia, economist Anthony Downs coined the "law of peak-hour expressway congestion" in 1962: “On urban commuter expressways, peak-hour traffic congestion rises to meet maximum capacity.” Congestion is natural and to be expected. If you add more lanes, you attract what is known as "induced demand," where traffic grows to fill the available road space.

Inrix claims that this is expensive. "Congestion cost the U.S. more than $81 billion in 2022, U.K. drivers nearly 9.5 billion pounds, and German drivers 3.9 billion Euros." They calculate the cost by multiplying the hours lost sitting in cars by the "hourly values of time" from the U.S. Federal Highway Administration, adjusted for inflation: $16.89 per hour in the U.S., 8.83 pounds per hour in the U.K., and 10.08 Euros per hour in Germany. These are weirdly low numbers given the cost of driving; parking in London or New York probably costs more than they earn per hour.

But time and money are not the costs of congestion—they are the costs of choices that have been made. I live in Toronto and was surprised to see it was considered congested. After all, I zipped downtown yesterday in a new protected bike lane that wasn't congested at all. But then Inrix isn't concerned about people on bikes, on foot, or on transit. It is only looking at people in cars.

Writing in Resilience, author and editor Bart Hawkins Kreps noted that in the most congested city, London, only 20% of the population commutes by car. In New York City, only 45% of households own a car, and fewer commute. In congested Paris, number three on the list, the government does everything it can to get people out of cars and into transit or on bikes. Hawkins Kreps suggested that with so many people walking, biking, or taking transit in the most congested cities, the focus on cars is misplaced.

"Arriving at a good estimate of the time non-drivers lose to traffic congestion is difficult, but that doesn’t make the losses any less real. Take, for example, all the time pedestrians spend waiting at traffic lights while autos either speed or crawl through intersections. Think of the extra time pedestrians must spend walking out of their way to get to a relatively safe place to cross a busy road and then doubling back to their destination. Think of the time public transit users must wait while their packed buses or trams are stalled behind private cars, which each carry one person."

That doesn't begin to cover the time it takes to walk anywhere in places designed for cars or where they have taken over. Hawkins Kreps adds a very useful term to the planning lexicon:

"But above all the people who don’t drive, but still need to get around, lose a lot of their time in getting past expressways, multi-lane arterial roads, and parking lots on the way to their destinations. Traffic congestion studies don’t even begin to quantify the time lost to all this 'induced distance'."

"Induced distance" is a wonderful term. I immediately thought of this recent tweet.

He tells Treehugger: "It’s widely recognized that if you keep adding more traffic lanes, there will be more traffic—that's 'induced demand.' Just as important is that as we clear space for wider roads and more parking, we push destinations farther apart—that’s 'induced distance.' As bad as induced distance is for drivers, it's even worse for the pedestrians who now need to walk much farther to get around in their formerly compact cities."

Induced distance is deadly, as people cross suburban arteries mid-block because traffic lights are so far apart. It makes walking unpleasant and difficult, as traffic lights are timed for healthy young people to get across the street in one light, while older or slower pedestrians have to stop in the middle or risk their lives.

Induced distance makes our suburbs uninhabitable for pedestrians and our cities uncomfortable. It's not just a North American phenomenon: In much of the United Kingdom, you have fences like these in Edinburgh where people have to walk between the fences and take two lights to cross the street, with very long waits between pedestrian signals. It's all designed to keep traffic flowing if you're a car.

Hawkins Kreps concluded:

"Studies like Inrix’s scorecard make for quotable listicles and reverse-bragging rights among the driving class. But beware when this skewed data is put forth as a basis for public policy decisions on transportation infrastructure."

If you are going to measure the time and costs of congestion, do it for everyone—not just the people in cars.