A nine-mile trip from the airport in Dhaka, the bustling capital of Bangladesh, to Justice Shahabuddin Ahmed Park, near downtown, can take as long as 55 minutes, according to Google Maps.
A trip of the same distance in Flint, Michigan, from the airport to the Sloan Museum of Discovery, takes about nine minutes.
While we might expect a slower drive in a metropolitan area of 20 million vs. a regional city of just 400,000, the difference in travel time isn’t due just to traffic or congestion, according to a new study that measures traffic speed around the world. Even at midnight, with few cars on the road, the trip in Dhaka—the slowest city in the world—is still 30 minutes, or three times as long as the trip in Flint, the world’s fastest.
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According to the study, published as a working paper by the National Bureau of Economic Research, the speed of travel in a city is only partially related to the amount of traffic on its roads. Other factors, such as the layout and quality of a city’s roads and natural obstacles like hills and rivers, play a significant role in how fast cars can drive. As a result, the study’s authors make a distinction between travel speed, a measure unaffected by traffic, and congestion, which is the interaction of speed and traffic.
“The slowest cities aren’t necessarily the most congested, and most congested aren’t the slowest,” says Prottoy Akbar, an economist at Aalto University in Finland and the lead author of the paper.
Akbar and his fellow researchers used data from Google Maps to analyze traffic in more than 1,000 global cities with populations over 300,000. Their data set excluded China and South Korea, because the app can’t collect data in those countries, while a few other cities, like Pyongyang, North Korea, were dropped because of unreliable data. They devised representative trips travelers would take in those cities—a commute from downtown to residential neighborhoods, for example, and or trips along the periphery from a home to a restaurant—and in 2019 ran millions of trips on the app, at different times of day and week. In India, for example, they collected data for 66 million trips; in the U.S. it was 57 million.
After crunching all that data, they found the biggest predictor of travel time in any given city isn’t the size or age of the city, but the wealth of the country in which it’s located.
The fastest cities, according to the paper, are almost all mid-sized municipalities in the U.S.—like Flint, Memphis, and Wichita, Kans.—where highways are wide and plentiful. Of the 100 fastest cities in the world, 86 are in the U.S., including 19 of the top 20 (the exception is Windsor, Ontario, across the Canadian border from Detroit). Even relatively poor cities in wealthy countries are fast.
The slowest cities, like Dhaka, Lagos, and Manila, are almost all in the developing world where infrastructure hasn’t kept up with population.
“All cities with the fastest speed or uncongested speed are in rich countries, and all the slowest cities are in poor countries,” the authors write.
Congestion, however, is less straightforward. The most congested cities come from a range of rich, poor, and middle-income cities, and while they include urban centers in the developing world like Bogata and Mexico City, they also include New York City and London. What they all have in common is size: very large cities, unsurprisingly, have more cars on the road.
But it’s also possible to be a congested city with relatively fast travel speed, Akbar says. Nashville, Austin, Tampa, Houston, and Atlanta are among the 25% most congested cities in the world, but are all in the top 10% for travel time.
A major takeaway from the study, Akbar says, is that different cities need different prescriptions to improve travel times. In Dhaka, where Akbar grew up, the municipal government spent a lot of energy trying to reduce the numbers of cars on the road, regulating things like the hours restaurants could be open and banning slower vehicles like bicycle rickshaws from highways. But “that just means that you could, at best, make the speeds in the middle of the day look like speeds in the middle of the night,” he said. “Those sort of adjustments can only help so far.”
Often, Akbar says, city planners in developing countries will rely on traffic studies commissioned for cities in countries like the U.S. and France, where the needs and solutions may be much different.
He also notes that fast travel doesn’t necessarily make a city more attractive or desirable, and it could be a result of over-investment in infrastructure relative to its needs. Flint, the fastest city in the world, has lost half of its population since 1950. “The fastest city in the world is not the city to envy,” he says.
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