Powering the streetcars, part 2: From web to thread
When many people think of "overhead wires" for streetcars, they picture the dense net of heavy cables common to many older systems. Modern streetcars, however, use very thin, single wires that are almost completely invisible.
Boston is a good example of the old system. It has a system of "trackless trolleys" which use wires (but run without tracks, like buses). These have two parallel wires, each fairly thick, and suspended above the roadway by fairly closely spaced perpendicular wires. Wires connect with large, very visible connections. Near intersections, there are numerous crossing wires and numerous support wires attaching in all directions. The effect makes the area look like a spider's web is hanging above the street.
Over time, systems evolved to require fewer wires and fewer supports. Here is a more recent trolleybus system in San Francisco that still uses two wires, but the visual impact is much lower.
Unlike trolleybuses such as those above, the latest streetcar systems only require a single wire, again with widely spaced supports. Plus, where there are tall buildings or tree canopies, the wires virtually blend into the streetscape entirely.
I've deliberately selected photographs with visible wires. However, in many photographs the wires become nearly invisible. In fact, streetcar advocates have sometimes shown pictures of overhead wires to skeptical neighbors, only to be accused of Photoshopping the wires out of the picture. (The above images are not Photoshopped except to resize them and add sharpening, which makes the wires even move visible.)
If DC used wires within the L'Enfant City, most streets would look like the ones in Brussels or San Francisco. If you looked toward the opposite side of the street, the wires would blend in entirely. If you looked far down the street, you could see two single strands (one in each direction) with occasional crossing supports, but not enough to "spoil the view."
Furthermore, engineers have a lot of leeway in the way they support the overhead wires. If the visual impact is a design consideration from the beginning, they can do a great deal to minimize the visibility.
Still, the wires would be visible. This should not be a reason to reject wires entirely, as there are already plenty of visible items in the air around streets, such as streetlights, traffic signals, trees, awnings, and buildings. The biggest and most reasonable concern revolves around the major "viewsheds," such as the view from Eastern Market Metro up Pennsylvania Avenue to the Capitol.
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