You may have seen the meme floating about on Twitter and Facebook that compared the amount of space occupied by different modes on streets. Generally speaking, they show how much space is occupied by cars as compared to buses, people on bikes, and people walking. As I was driving through Atlanta recently, I wondered how much space was taken up by the urban interchange below as compared to other modes.
This interchange occupies more land than many cities’ central business districts.
This is where I-75 and I-85 split north of downtown Atlanta. It nearly fills the image. Atlantic Station, a large office, residential, and shopping complex, is dwarfed by this tangle of ramps.
To see how much land a similar split of rail transit lines would use, I looked at one in Alexandria, Virginia.
The DC Metro’s Yellow and Blue lines split here. A railroad track is adjacent to the right.
Note that I rotated the image to make comparisons easier. As you can see, more tax-yielding businesses and residences are in this picture than in the Atlanta image. Plus, more greenery is present to help fight the urban heat island that afflicts so many US cities, including Atlanta.
But what happens at a split of trails for cyclists and pedestrians?
This junction of two heavily-used commuter bike/pedestrian routes is hard to discern without the green highlighting.
The infrastructure nearly disappears. This is the intersection of the Mount Vernon Trail and the Four Mile Run Trail in Arlington, Virginia. Both see heavy commuter usage during rush hour, since Washington, DC is located just across the Potomac River to the north while various Virginia suburbs are located to the west and south. The George Washington Memorial Parkway, Amtrak/CSX line, and Metro run parallel to the Mount Vernon Trail here.
The enormous parking lot to the upper right serves Reagan National Airport. Airports are undoubtedly the worst land use gluttons of all (and not just for the runways).
Land use is an important issue in a dense urban environment. Space used for transportation is space that can’t be used for much else. Politicians and planners should take heed.
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It would be interesting to look at how many people are moved through the modes of transportation in those examples to compare efficient use of space in addition to relative amount of land used.
Urban heavy rail can move up to about 40,000 people per hour;
Intercity rail can move up to about 24,000 people per hour;
A road occupying the same space as two rail tracks can move up to 2000 people per hour.
Bike lane capacity seems to be 2600 bikes per 3.5-foot one-way lane.