Powering the streetcars, part 2: From web to thread

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Powering the streetcars, part 2: From web to thread

by David Alpert • September 22, 2009 3:16 pm

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.

Not a very pleasing wire system. Photo by bradlee9119.

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.

San Francisco. Photo by infosnackhq.

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.

Brussels. Photo by Ralph Garboushian.

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.

Tomorrow, we'll look at the hybrid solution DC is likely to adopt.

26 comments

Tags: DC, NCPC, overhead wires, streetcars

Powering the streetcars, part 3: The hybrid solution (Sep 23, 2009)
Powering the streetcars, part 1: The dilemma (Sep 22, 2009)
Overhead wires and beautiful streets can coexist (Oct 30, 2009)
Streetcars preserve, not spoil, historic cities (Jun 24, 2010)
Streetcars are historic preservation in Georgetown (Sep 23, 2010)

David Alpert is the Founder and Editor-in-Chief of Greater Greater Washington and Greater Greater Education. He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He loves the area which is, in many ways, greater than those others, and wants to see it become even greater.

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The picture of the Boston wires is just a bit misleading, since it's not only a 3-way t-intersection, but there's also a turnaround for buses at that intersection (IIRC).

by ah on Sep 22, 2009 3:28 pm • link • report

Here's a picture showing the Boston trolleys on a straighter segment. It's still very web-like.

by David Alpert on Sep 22, 2009 3:30 pm • link • report

Should be emphasized that the first two photos are for trolleybuses, which always have two wires. Streetcars always require only one contact wire. Sometimes that's supported by a catenary wire, but for low-speed operation it's really not necessary.

Junctions and turns really increase the visual impact. We should avoid having wires there.

by Michael Perkins on Sep 22, 2009 3:31 pm • link • report

Could you find a picture of the better systems at points when they make turns on roads or various routes intersect like the first pictures. I've spent significant time walking around SF and a good portion of the two wire system is much uglier than that picture... not to say that its not reasonable, but misleading comparisons don't help anyone.

by dd on Sep 22, 2009 3:43 pm • link • report

For example, here's a view of single wires where the T line intersects with the N line at 4th & King st in SF. Much better than the Boston pictures, but far from invisible. A picture with an still camera rather than streetview would highlight the wires much more.

View Larger Map

by dd on Sep 22, 2009 3:50 pm • link • report

So costs and potential maintenance issues are the main concern with burying the wires?

From a cost standpoint, does anyone know how the hybrid solution compares with the alternatives? It would obviously depend on what approach is taken where, but I wonder how much will be saved by going this route.

by Vik on Sep 22, 2009 3:55 pm • link • report

I detect a bias in this discussion? Somehow overhead wires are unacceptably ugly, but we tolerate all sorts of other visual blights, from overhead traffic lights to bollards and huge concrete barriers everywhere.

While I don't think aesthetics is an entirely invalid concern, this argument smacks of a back-door way to shut down streetcar projects entirely.

by Distantantennas on Sep 22, 2009 3:55 pm • link • report

I'm not saying overhead wires are unacceptably ugly. I'm just calling out the claim that modern wires "blend in entirely" to the streetscape. They are very visible. Claiming they aren't merely weakens the entire argument.
Given a cost benefit analysis, a few ugly wires in the air may be better than a much more expensive underground option or no streetcars at all, but the wires are still ugly.

by dd on Sep 22, 2009 4:08 pm • link • report

BTW, for a really directly comparison, you can go a block away from my above image to 4th & Townsend to see an older 2 cable system that SF uses for MUNI busses. The new system is definitely an improvement, but still highly visible.

View Larger Map

by dd on Sep 22, 2009 4:13 pm • link • report

But, Dave, that's a curved segment with a second set of wires so buses can pass.

How about this one?

http://www.flickr.com/photos/cem6357/429312350/in/set-72157600013398796/

Or, if you like the less-wire style of SF, go nuts!

http://www.urbanrail.net/am/snfr/sf-streetcar-01.JPG

by ah on Sep 22, 2009 4:17 pm • link • report

Yeah, you definitely shouldn't show "trolley"bus photos (they're buses).

See, buses need two wires, because electricity needs to continue traveling. That is to say, it needs to go into the vehicle and back out of the vehicle ... a complete circuit. Another way to understand this is a ground ... electricity needs to go into the ground.

But with trolleys, you only need one wire. The rails, which are obviously metal, can carry the electricity to the ground. Trolleys that use a single-wire pantograph are made so that the current goes through the wheels, to the rail, and into the ground.

Of course, trolleybuses also have bow collectors, while trains have pantographs. Pantographs are smaller and, in my opinion, much less ugly.

The other issue is holding the wire up. Many systems in fact have sets of wires: one set is linked directly to the things that keep them up, while the wires carrying the current are tied to the aforementioned wire. Among other things, it allows the actual current-carrying wire to straight, but it also means it carries less tension.

Then again, it's hard to argue with that photo from Brussels. That's pretty slick.

by Tim on Sep 22, 2009 4:37 pm • link • report

I'm pro streetcar, and pro (some) wires, but claiming the wires in Brussels are nearly invisible is simply untrue. Look here, here, and here.

Personally, I think the utility outweighs the aesthetic considerations, and a hybrid wire/battery system makes sense for DC, but minimizing the aesthetic ramifications really doesn't help the cause.

by jcm on Sep 22, 2009 4:41 pm • link • report

@Distantantennas

It's not a biased discussion, because of the legal implications. There's a law against overhead wires. There's not a law against bollards or traffic lights or huge concrete barriers.

I certainly think the negatives for wires are tiny and vastly outweighed by the positives that streetcars and light rail offer, but those are just my personal biases and are not codified in law. The overhead wire ban is.

by Alex B. on Sep 22, 2009 5:07 pm • link • report

The Brussels pictures aren't jarring at all. The wires aren't nearly invisible, but I'm not going to complain.

And the NCPC, while reviewing plans for the 11th St Bridges (which will connect to an overhead freeway) makes remarks about overhead wires? I live on the Hill and to my south is the SE-SW Freeway and to my west is the I-395 canyon. Wires are going to ruin everything?

by HM on Sep 22, 2009 5:11 pm • link • report

None of those pics jcm linked to seem like deal breakers to me. And even the claim of down Penn Ave from Eastern market would not ruin the average sightline of a car or a pedestrian as they would be on sidewalks or the street and not in the median.

by NikolasM on Sep 22, 2009 5:16 pm • link • report

This is a great picture, jcm. Yes, you can see the wires, but they are less intrusive than the traffic signs.

by BeyondDC on Sep 22, 2009 5:26 pm • link • report

Another consideration is that street trees may need to be trimmed to keep from interfering with the overhead wires, just like overhead electrical and phone wires. That is one of the arguments for burying electrical wires in urban areas. However, the streetcar wires usually run over the center of the roadway where tree canopy is somewhat less of a concern.

It would help to visit some existing examples. Cities like Salzburg and Rome have overhead tram wires along some very historic streets, and if you are there in person they aren't very noticeable. The tracks are more noticeable.

This article has a good review of ground-level supply systems, including the one in Bordeaux, France which has gotten off to a rocky start.

by Laurence Aurbach on Sep 22, 2009 5:28 pm • link • report

Its not about system, its about what the wires are doing. On straight parts of mass ave, the Boston (cambridge actually) system is also nearly invisible. Any system in which routes cross, or there are curves will be very obvious.

by J on Sep 22, 2009 9:47 pm • link • report

Trolleybuses (which have rubber tires) require two wires that don't touch each other - it's a bit of an engineering miracle that they ever developed practical trolleybus intersections, and they do look a lot like spiderwebs.

Aerial visual obstruction at intersections is a non-issue with a single-wire catenary (which requires metal tracks) in this day and age because of batteries and supercapacitors. Lower the catenary before the intersection, raise it after. Every intersection uses a few pennies of lithium ion charge cycle. Trolley poles are apparently difficult to re-attach until someone implements a robotic method of doing that, but catenary bars are easy to raise.

by Squalish on Sep 22, 2009 11:04 pm • link • report

In Philadelphia, I've questioned people regarding what they think about the trackless trolley wires. The usual answer is, "what wires"? The average person neither sees them, thinks about them or ever notices them. The only exception might be an intersection that has what's called "special work" where multiple lines converge.

I've discovered that most people don't know a trackless trolley from a bus. The only time they might become consciously aware of the overhead wires or the trolley poles on the roof is if one comes off the wires. Otherwise, they simply think it's a bus.

People that bring up visual pollution are really making a big deal over nothing. I'd rather have those thin wires than clouds of exhaust pollution and noise from Diesel buses. And it's a good way to reduce our dependency on foreign oil. Electricity can be generated locally by many clean methods.

by TransitJeff on Sep 23, 2009 12:35 am • link • report

The overhead wire has a pictorial description of the difference between catenary and trolley wire. Visually, the difference is striking.

http://theoverheadwire.blogspot.com/2009/09/catenary-and-trolleywire.html

by Michael Perkins on Sep 23, 2009 9:24 am • link • report

P.S. The ETB system "in Boston" actually operates in Cambridge, Belmont and Watertown, Mass.

And the "visual pollution" results in no noise- or air-pollution coming from the bus itself. Electricity can be produce in many ways, some of them can be quite non-polluting.

The District, which was built on a swamp, needs to get over itself. If Quonset huts on the Mall were okay in the fight against Hitler and Tojo, then cantenary should be just fine in the fight againt climate change and Hugo Chavez.

by Erik G. on Sep 23, 2009 1:06 pm • link • report

Some of these jokers dont seem to realize that wheter troley coach of streetcar or light rail and rapid transit
There is no fumes when you're using any of these methods as a power source Why did light railsystems make a comback in a lot of cities?
1 .The Arab Oil Embarog becasue of the Yom Kippur war OPEC
putsa oil embargo on the USA and it prompts a so-called "energy Crisis"
2 . At the same time Mr>Bradford Snell comes into play That General Motors and natioan City Lines took us for a ride
and conspiered with National City Lines to get rid of streetcar systems in the name of "progress' and it was a ploy to to make a quick buck
# when The 1973 Embargo hit us remaning Cities who had retaied streetcar lines like Boston San FRancisco Philadelphia New Orleans Shaker Heights Ohio and Pittsburgh Pa. Were thanking thier lucky stars they held on to thier systems

by Fred M Pohl on Sep 24, 2009 8:04 am • link • report

I have to say, I'm not all that bothered by the concept of overhead wires in DC. At least not for streetcars. Honestly I think the solution to this problem is to use overhead wires for streetcars.

As for vistas in the city, I think streetcars can play a positive role. It's always great to capture a tram in front of a monument. And the wires are not always impediments to that.

For instance, on a trip to Sacramento last year, I snapped this picture:
http://1.bp.blogspot.com/_IleclKMZ1Mg/SSOVJQn690I/AAAAAAAABa0/gWYF58p5HoA/s1600-h/Railvolution-08+123.jpg

I haven't done anything to the picture with software.

by Matt Johnson on Sep 24, 2009 10:31 am • link • report

The use of trees (shady trees) helps hide overhead wires. Seattle and Portland run the rails down the side of the street leaving a space for parking. Shade trees will grow over these wires thus blocking the view except at intersections. Central boulevard trees also help. This the way to go.

by Richard C. DeArmond on Sep 24, 2009 5:47 pm • link • report

Tim wrote: "trolleybuses also have bow collectors, while trains have pantographs".
Actually, trolleybuses can only use trolley poles.
Some streetcars also use trolley poles.
Streetcars--and "light rail vehicles", which are more or less the same technology--can also use pantographs or bow collectors.

by Stanley on Sep 7, 2011 3:38 pm • link • report