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Thread: How much of a city is used by cars?

  1. #1
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    How much of a city is used by cars?

    Greetings! This is my first post here, and I'm here because this looks like a forum where people know what they're talking about. I'm looking for some specific information which I know I've seen out there, but right my Googling abilities are completely failing me. So perhaps somebody here knows the answer.

    I'm looking for a reputable source of data as to what percentage of the surface area of a city is used by automobiles (for roads, parking lots, gas stations, driveways, et cetera). It would be great to have a city-by-city breakdown for this data, but more generalized statistics would work as well, provided that they're from a respectable source.

    Can anybody help me out here? I'd much appreciate it! Thanks!

  2. #2
    Cyburbian DetroitPlanner's avatar
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    It depends on the city and its car ownership percentage. Also areas where there is a lot of trade or manufacturing will need more infrastructure to help provide for the movement of stuff; much of that movement is done by truck. One thing that may bias your sample are areas that require multi level garages such as found in cities with medium to large sized downtowns. What appears as square footage in terms of land area is much less than the amount of space you can use to park cars there.

    Keep in mind that buses and bike use that infrastructure too so it is not devoted strictly for cars.

    Driveways and parking lots, gas stations as a portion of land area? This would be hard to get as well.

    How about multimodal areas such as train stations with kiss and ride or airports with centralized structures?

    How about other car related businesses such as auto dealers, car washes, auto parts stores, drive thru restraunts and banks, do they count more than others?

    What about parking lots that are not surfaced? (dirt) would they count?

    I doubt it there is this stat out there. It would be too complex to put together.
    We hope for better things; it will arise from the ashes - Fr Gabriel Richard 1805

  3. #3
    Cyburbian safege's avatar
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    I agree about the park n' rides of whatever multi-modal use. In Minnesota, the suburban park n' rides are full or nearly full, and new bus riders from parking lots are outpacing new riders from bus stops by 2 to 1.

    So, these parking lots in the suburbs are either a surplus, or a negative number, depending on how the calculation is made.

    I'm not a planner, but that is my 2 cents.
    Psychotics are consistently inconsistent. The essence of sanity is to be inconsistently inconsistent.
    -Larry Wall

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    Thanks for the responses. I might have given the wrong impression in my initial post, however: I'm just looking for the percentage of a city's surface areas that is typically used by automobiles at all, not the "share" of the car's usage of roads & such, versus other forms of transport. I know that such statistics have been gathered, because I've seen them published before. I just for the life of me can't seem to find where.

    To give you a notion of the kind of analysis I'm looking for, I recently did it for a 16-block area of Portland's Pearl District, near where I work. This is a very transit-oriented district, with a streetcar, several buses, heavy bicycle usage, and a large parking lot that is turned into a Farmer's market once per week. All that matters for my purposes, however, is whether or not a given surface is ever used by cars. So, the basic street layout accounts for 27% of the surface area, and parking lots (both open-air and single-purpose garages) and gas stations account for another 27% of the surface area. Above-ground or underground parking doesn't count, but surface-level parking absolutely counts, whether or not it feeds into other transit modes. I suppose that mechanic shops might be counted as well, but that seems to be getting too fidgety. Anyhow, it's a reasonably simple analysis that somebody with a better GIS program than I ought to be able to do quite quickly.

    Nobody has encountered any such statistics?

    Thanks!

  5. #5
    Cyburbian AubieTurtle's avatar
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    I'll see if I can dig up the source article but I remember a study that came out a few years ago showed that over 60% (yes, SIXTY PERCENT) of the land in Atlanta's central business district was dedicated to the automobile in some way or another. I'm going to guess that has dropped in recent years with surface lots being replaced by buildings. I'm not sure how they handled situations such as a condo built on top of a parking deck but regardless of the counting method, cities do have a surprisingly high amount of the ground dedicated to the automobile.
    As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron. - H.L. Mencken

  6. #6
    Cyburbian boilerplater's avatar
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    From Suburban Nation:
    "Between one third and one half of urban America's land is typically dedicated to the drving and parkig of vehicles. In Los Angeles, that ratio jumps to two thirds. Houston provides the equivalent of 30 asphalt parking spaces per resident."

    The passage has a footnote that states that the situation in Houston is starting to change with investments in downtown housing. I'd bet that the numbers for LA have also changed since the book came out, just going from personal observation on a visit to downtown LA last Spring.
    Adrift in a sea of beige

  7. #7
    Cyburbian
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    One way to get the information is through GIS analysis of USGS Landsat data or aerial photos. My guess is that the larger the study area the more you are going to need some serious GIS support. I attached a couple documents that might prove useful although is focuses on all impervious surfaces, which are mostly roads and pavement, but also a lot of roof area.

    Sorry for the scale of the graphic...

    Attached Files Attached Files

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