Great Cities Don’t Have Much Traffic, But They Do Have Congestion

Image: Tomtoms 2013 via Cityclock
Places with less traffic have more congestion. Graphic: City Clock

Here’s a great visualization of what cities get out of the billions of dollars spent on highways and road expansion: more traffic.

Justin Swan at City Clock made this chart showing the relationship between congestion levels, as measured by TomTom, and car use. (Yes, it has no X axis — here’s Swan’s explanation of how to read his chart.) The pattern that emerges is that the places with the most traffic and driving also have the least congestion.

We know from the work of Joe Cortright that the traditional definition of congestion is a poor way to measure people’s ability to get around their city — because it doesn’t reflect the actual time people spend traveling. Drivers in Dallas and Houston may stew in gridlock less than people in other cities, but they spend more time on the road.

Swan notes that the most congested places are also the places where people have good travel options that don’t involve driving. His chart suggests that car congestion itself is not the problem that needs to be solved — as long as there are other ways to get around, in a congested city few people will actually have to sit in traffic.

17 thoughts on Great Cities Don’t Have Much Traffic, But They Do Have Congestion

  1. I completely agree that car congestion can be a sign of a healthy city.

    However, I’d like to point out that the center of Vienna has very little car congestion because 1) blocks and blocks and blocks of it are pedestrian only (no cars at all! so no congestion!) Inside the entire inner ring there is very little congestion because it’s been divided into 5 pie shaped wedges, and cars cannot go directly from one wedge to another. (They must go out of the ring and then enter the pie wedge they want to.) This results in minimal car traffic, making it very pleasant for walking and bicycling (and even horse-drawn carriages.)

    The inner ring of Amsterdam is also uncongested, with few cars on the roads. Walking and biking paradise. Many neighborhoods outside the inner ring in Amsterdam are also nearly car-free because imposed dead-ends allow no through traffic for cars, only access for those who live/work/shop there. (Bikes and pedestrians can travel directly through, of course.) The result is remarkably dense, calm, quiet, livable neighborhoods.

    Prague has a great deal of car-free space in its historic area and is on its way to expanding it. (Outside the car-free area, the cars can be intense.)

    Berlin is fairly uncongested in terms of cars, but this is due largely to quite low levels of car ownership in that city (and the fact it is still not at its WWII peak population levels.) It is an easy place to bike and walk, and of course has excellent transit.

    Venice is completely uncongested with cars. (Now tourists, that’s another matter.)

    So it is possible to achieve very dynamic, livable, dense, active cities with both little traffic and little car congestion.

  2. I think I get the point, thanks to the writing in the article and my general knowledge of transportation, but this infographic is…terrible.

    I read his explanation and follow it, more or less, but it is a very confusing chart.

  3. The point isn’t that you need car congestion to be a healthy city, but that in a healthy city roads made available to cars are well used i.e. there is congestion.

  4. @EastBayer: I cannot understand the graph, either. Each city seems to be a point; the vertical dimension measures which – %by car or congestion? For purposes of plotting a city, it can’t be both. The horizontal dimenstion seems to measure something – there’s *change* as you go left to right – but it’s not clear what. A complete waste of space.

  5. this graph is sooo void of pertinent information not sure why it is published. It misses many important factors such as regional gas prices, population densities, regional topography, land use laws and etc. The influence of these factors on road development and usage is huge.

  6. A line graph with two variables plotted on y-axis but no variables on the x-axis is incomprehensible to me. Why not plot congestion on the y-axis, %age travel by car on the x-axis, then do a proper scatter graph with a best-fit line?

  7. From this graphic, it appears that Dallas, with 70+% travel by car is the place to be given their low congestion.

    I have to agree with “incomprehensible” and “void of pertinent information”.

    Wait, no. I read it wrong. ~95% travel by car, very low congestion, lower even than the greens, reds, and blues.

    What was this about again?

  8. I think I understand the graph. I’ll explain. The cities are arranged left to right in decreasing order of “percent travel by car” — and spaced equally, though not all cities are named (the linked article says there are 74 cities). That’s the green. So restricted to the green, it’s just a bar graph. But then, in addition, for each city they also plot the city’s “congestion level” (also measured vertically) as a red dot inside that city’s horizontal position in the bar graph. Terrible, I know. One obvious problem is that the horizontal axis has a non-linear distribution of “percent travel by car,” because it’s spaced equally by city as opposed to the value. Yes, a scatter plot would make a lot more sense for this data.

  9. The Miami data can’t be right. Try driving between downtown, Coral Gables, South Miami, and Coconut Grove any time near commute times. You will be sitting still a lot.

  10. It doesn’t take all that large of a percentage of people in a city using cars to congest the roads. At any given time in NYC more than 90% of the cars people own are parked, but the ones in use easily fill up the roads.

    Point of fact, if everyone in NYC wanted to get around by car, there just wouldn’t be the room for it.

  11. By definition, any visualization that needs an explanation of how to read it has failed in it’s purpose.

  12. FWIW, the point of all this is that a healthy city is one that does not depend on cars, does not worry much about cars and does not waste money trying to “fix” car congestion. Nevertheless, cars remain popular because, when they work, they are very convenient.

    This has two consequences. 1. In healthy cities, what little space is set aside for cars is filled by those who feel they need to use cars anyway 2. Consequence 1 doesn’t matter that much.

    The bottom line is that “congestion”, like zombie apocalypse, gets lots of attention despite its irrelevance. The media, and policy makers, really do need to focus on something that matters instead.

  13. This is a great data visualization? No, this is a terrible data visualization: Two y-axes on different scales and no x-axis! His explanation makes no sense: “The purpose of using two separate lines was so that up was positive and down was negative for both (i.e. instead of left to right for one and up and down for the other).”
    The graph is uninterpretable, and the trend lines are meaningless.

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