Atlanta streetcar - why not third rail? (Smyrna, Dallas: 2013, maintenance)

[netdragon]

So, thought I'd walk one block from my office and check out the streetcar line, since I haven't checked it out in a while, and was wondering why there is overhead wire, not a third rail. They had excavated the road anyway. Is it cost of the train stock, safety, car crossing bumpiness, infrastructure, maintenance, or something else? From a safety perspective, I figure the third rail could be set up in a way that someone couldn't have zapped themselves.

[MattCW]

There are systems that allows a third rail to be laid in the middle of the tracks, the separate conducting segments don't power on until the vehicle completely covers them to eliminate the electrocution risk, but there's only a few systems that use that and they would likely drive the price up and possibly delay the project.

[magnetar]

Originally Posted by netdragon

... was wondering why there is overhead wire, not a third rail.

Basically every light rail system in the United States uses an overhead catenary wire, regardless of when they were built. If I had to guess it's probably because Atlanta was under extreme pressure to keep the cost down, and using a standard streetcar vehicle allowed them to do that.

In about 5 minutes of Googling I found that all of the 10 largest light rail systems in the country are designed this way.

Boston
SF
LA
San Diego
Portland
Philadelphia
Dallas
Denver
Salt Lake City
St. Louis

[netdragon]

Magnetar, you hit it right on the head when you said "regardless of when they were built" because I consider overhead wire old-fashioned and tacky, though I grew up in the Northeast where overhead wire trunks of any type were typically buried during any major road work (frost causes major issues) so I think I have a different perception of overhead wires than people from the South. I'm guessing you're both right about cost, but I think the biggest cost is when a train needs to support both modes. Metro North's trains from New Haven, CT to Grand Central support both caternary (in CT and Westchester County) and third-rail when they enter far enough into NYC. I think by Bronx it was already third-rail if I recall correctly from the maybe 50 times or so I rode it into NYC and definately by Harlem's 125th street station it had no caternary wires. I remember a discussion to convert them to third-rail only because the cost of supporting both is higher. They had the break-down for each mode as well, by itself, for the stock and they were pretty comparable, but it has been so long that I can't remember what the reftrofitting cost estimates for the lines in CT were (removing the caternary wire and putting in the electrified rails).

[MattCW]

Supporting both modes using Metro North as the example isn't quite so cut and dry. Metro North has "issues" because the catenary is high voltage AC while the third rail is low voltage DC. If the catenary were 750 volts DC like the third rail, there wouldn't be any real problems, just the power would enter by a different means but would still be treated the same internally. With AC, you have a large transformer to worry about as well as insulating the higher voltage and you have to rectify it at some point. I wouldn't expect Metro North to ever go completely third-rail, they'd have to lay it on four tracks from roughly New Rochelle, all the way to New Haven, and Amtrak wouldn't be happy either and could make a lot of noises about that.

But back to the topic, what do you mean by overhead wire trunks? Do you mean the overhead lines for the streetcar systems were buried?

Frankly, I agree that overhead wires are not what to pursue in the future for in-street vehicles. Eliminating the overhead spiderweb would also help the anti-transit issue and give the opponents one less thing to worry about...though they'd probably start spouting off about electrocution or something.

[netdragon]

Originally Posted by MattCW

But back to the topic, what do you mean by overhead wire trunks?

I meant overhead electrical and communications trunk lines. They tend to get tunneled whenever possible in the Northeast on major roads, and the telephone poles removed, which looks more aesthetically pleasing. It only gradually happens, when the opportunity arises for existing roads, such as lane excavations for other reasons. Here, I've seen them redo roads in ways that would warrant tunneling the wires and yet they just move the poles around here. Concord Rd in Smyrna right now, for instance. I didn't understand at first why that happened, until someone reminded me that we don't get ice storms here like in the Northeast.

[cqholt]

Overhead lines are safer for pedestrians, cyclists, and drivers.