Overhead Wires Vs Third Rail

[frischee112]

Which one is better? I know for the most part overhead wins for intercity and commuter but third rail has one advantage: no visual intrusion (it blends in with the rail). In modern systems what is better?

[trainmaster611]

Third rail has lower capital costs than overhead wires. That's where the advantages end.

Third rail is obviously puts more people in danger since it's at ground level so you have to make sure the entire line is grade separated. Third rail also has a lower top speed for its trains than overhead wire. The only thing I don't know is how operating costs compare. But because of the reasons I mentioned, third rail is generally only advisable for metro (subway and el) operations. You'll see it on mainlines like the LIRR and Metro North's Hudson Line but in those cases, it's more a hindrance than anything else.

A quick google search even brings this up: http://en.wikipedia.org/wiki/Third_rail ... advantages

[amtrakowitz]

Third rail has lower capital costs than overhead wires. That's where the advantages end

No, that's not where they end, and there isn't lower capital costs in all cases. Third rail allows lower clearance under bridges and tunnels. Maintenance vehicles do not have to bring crews to the air to repair electrification infrastructure. Electric current collection on trains is also simpler to reach, being located on the wheel trucks (usually) versus on the roof.

Third rail obviously puts more people in danger since it's at ground level so you have to make sure the entire line is grade separated

Plenty of grade crossings on the Long Island Rail Road and Metro-North Railroad in their third rail territory. There are even grade crossings at certain locations on the CTA. In no cases have I heard recent reports of people being electrocuted by third rail.

You'll see it on mainlines like the LIRR and Metro-North's Hudson Line but in those cases, it's more a hindrance than anything else

What does it hinder? The trains still run every day. There has been third rail dating from the time when the majority of platforms on both railroads were low-level. The Chicago, Aurora and Elgin interurban also combined low platforms with third rail, IIRC, as did numerous other interurbans electrified with third rail.

Third rail is on Metro-North's Harlem Line as far north as Southeast station (formerly known as Brewster North). Before that, the northernmost extent of third rail was North White Plains; it was Metro-North that built the extension of third rail to Southeast.

And BTW, not all third rail is at ground level. There are instances of overhead third rail; formerly on the B&O main line in Baltimore, and extant within Grand Central Terminal in NYC (currently disused, since there are no all-electric locomotives on Metro-North).

Whomever wrote the Wikipedia article injected a lot of opinion rather than fact.

Deciding on choosing third rail or overhead therefore depends on the needs of your system. There is no practical advantage if your system is at 750 volts DC between third rail and overhead wires, even in cases of street running (where one can use conduit third rail—no danger experienced with such systems, either with the Third Avenue Railway in Manhattan or DC Transit's streetcars). Higher-speed railroads can use high-voltage AC overhead wires, where fewer substations per mile and no need for rectifiers to transform AC to DC do indeed save capital and maintenance costs.

[electricron]

How about using no wires at all, what's so wrong with self-propelled diesel powered DMUs?

FWTA, The T, is presently studying whether to use Stadler DMUs over 7 miles of a fairly straight city street, East Lancaster Road, vs using light rail or streetcars. It helps somewhat that East Lancaster is already a six lane street with up to 60 feet wide median to make this size train more viable. If diesels can be used on a city street, surely diesels remain viable for intercity trains.

[trainmaster611]

Most of my information is just from research and whatnot (not from the wikipedia article though, I just like to use throw that in as a good summary sometimes). Hopefully you have a better source you could share?

For the sake of brevity, I'll respond to the points I have issues with. Otherwise, I'm in agreement or I don't have an opinion on the matter.

Plenty of grade crossings on the Long Island Rail Road and Metro-North Railroad in their third rail territory. There are even grade crossings at certain locations on the CTA. In no cases have I heard recent reports of people being electrocuted by third rail.

Yes but those crossings are legacy hold-overs. Nobody who is building third rail in the modern day is going to build an at-grade third rail crossing because of the safety risks (except for the Skokie line probably because it was a legacy line and they didn't have the money for grade-seperation). I can only imagine that insurers would go ballistic if they found out someone was trying to construct a new third rail crossing. Even the CTA is trying to eliminate all of their at-grade crossings. And I can guarantee you the only reason the other crossings aren't being grade-separated is because of the costs involved in doing so.

And you probably don't hear about it because it isn't something that makes big news. Just a quick google search turned up this NYC death in April 2010 and electrocution on the CTA in August 2011.

What does it hinder? The trains still run every day. There has been third rail dating from the time when the majority of platforms on both railroads were low-level. The Chicago, Aurora and Elgin interurban also combined low platforms with third rail, IIRC, as did numerous other interurbans electrified with third rail.

How about when it snows. All forms of rail are prone to closures during severe weather but third rail moreso than others. Washington's Metro has been known to shut down the above-ground segments because of storms. You'll notice LIRR's on-time performance plummets and cancellations rise in the winter. Overhead wire tends to be less prone to this.

Also, I don't think interurbans from the pre-depression era are an example we should be following today. The third-rail on the CA&I was a big safety hazard for the railroad. You have to keep in mind that interurbans were built with cheap capital costs in mind which made third rail very attractive.

I've done research in the past and of course it may be faulty. Again, if you have any sources please share them because I'd be interested to read them.

How about using no wires at all, what's so wrong with self-propelled diesel powered DMUs?

Because electric operation is better than diesel operation in almost every category except capital cost. Electric operation is cheaper than diesel operation (including maintenance and energy costs). Better acceleration. Less energy intensive. Less pollution. Less noise. Diesel is less prone to system-wide contingencies but that alone isn't an operational reason to build a diesel line. Excluding capital costs (which is a very big factor) there isn't really any reason to install a diesel system over an electric system.

[electricron]

Because electric operation is better than diesel operation in almost every category except capital cost. Electric operation is cheaper than diesel operation (including maintenance and energy costs). Better acceleration. Less energy intensive. Less pollution. Less noise. Diesel is less prone to system-wide contingencies but that alone isn't an operational reason to build a diesel line. Excluding capital costs (which is a very big factor) there isn't really any reason to install a diesel system over an electric system.

If what you state is true, why are just about every transit agency in America using diesel locomotives for "commuter" rail? Even those that run some trains under electric lines, MBTA and MARC. Even in Europe, where there's far more tracks with electric wires overhead, you'll still find many passenger trains using diesel locomotives. The capital costs to install electric wires above tracks isn't as cheap some suggest.

[trainmaster611]

We've had this conversation before.
http://www.railroad.net/forums/viewtopi ... 51&t=85570

If what you state is true, why are just about every transit agency in America using diesel locomotives for "commuter" rail?

Because of capital costs. The ridership on most commuter lines isn't enough to justify electrification.

Even in Europe, where there's far more tracks with electric wires overhead, you'll still find many passenger trains using diesel locomotives. The capital costs to install electric wires above tracks isn't as cheap some suggest.

I don't know anything about MARC but I already answered your MBTA question in the other thread. But even in Europe, there are unelectrified lines and often times they branch off of electrified territory. If you have a train that's going to be running from electrified territory to a point that's unelectrified, depending on the distance or the kind of rolling stock you're using (MU versus locomotive hauled) it's easier to just use diesel the entire way. But if you're staying entirely within electrified territory, there's no reason to use diesel.

Regarding your last point, you're right, electrification is pretty expensive (you even answered your own question). I've heard $3 million/mile thrown around but Caltrain's electrification is supposed to be more expensive.

[amtrakowitz]

How about using no wires at all, what's so wrong with self-propelled diesel powered DMUs?

Yes, those would be perfect for a subway operation [/sarc]. And where they're feasible, they're kinda thermodynamically less efficient.

Most of my information is just from research and whatnot

Then I don't see how your research made you cite one solitary advantage of third rail, and that related to capital cost rather than lower tunnel clearances and easier access for maintenance. What with having substations every two miles or so, and those substations including rectifiers to change AC from the grid to DC, I don't see how it's cheaper at all. It's most likely on a par with other forms of electrification, especially when it comes to operating costs.

Yes but those crossings are legacy hold-overs. Nobody who is building third rail in the modern day is going to build an at-grade third rail crossing because of the safety risks (except for the Skokie line probably because it was a legacy line and they didn't have the money for grade-separation). I can only imagine that insurers would go ballistic if they found out someone was trying to construct a new third rail crossing. Even the CTA is trying to eliminate all of their at-grade crossings. And I can guarantee you the only reason the other crossings aren't being grade-separated is because of the costs involved in doing so

No, "legacy holdovers" is opinion. It certainly does not explain why Metro-North retained the grade crossings when extending the Harlem Line electrification from White Plains to Southeast. It's not the railroad's responsibility to find other easements across their right of way; that would be the role of the division of the department(s) of transportation that deals with roads and streets.

The last grade crossing on the NYC subway system, on the Canarsie Line (L train) was on East 105th Street, adjacent to the station; it was closed by removing the crossing and creating two dead ends, severing the street. Even the Northeast Corridor, especially in Elizabeth NJ, severed streets in this fashion, particularly DeHart Place and Grove Street. That's the cheap way to do it; but it doesn't make a neighborhood any more walkable or drivable.

Also, the Skokie Swift line was part of an interurban (the Chicago, North Shore and Milwaukee) originally electrified with overhead wire. The CTA didn't have to get rid of that overhead wire system, which cost the public extra money. The railroad is not more dangerous due to the third rail that is there now.

And you probably don't hear about it because it isn't something that makes big news. Just a quick google search turned up this NYC death in April 2010 and electrocution on the CTA in August 2011

Neither of those happened at grade crossing locations. One was a case of trespassing as well; and that death could have happened due to being struck by a train. Railway workers face many other hazards besides; when working with overhead wire, the need for grounding is yet greater due to the higher potentials.

How about when it snows. All forms of rail are prone to closures during severe weather but third rail more so than others. Washington's Metro has been known to shut down the above-ground segments because of storms. You'll notice LIRR's on-time performance plummets and cancellations rise in the winter. Overhead wire tends to be less prone to this

That's more of a matter of culture than anything else, and the culture at the MTA and WMATA seems to have degraded over time. PATCO has operated through snowstorms that would shut down LIRR and Metro-North (whose predecessors, IINM, operated through snowstorms in the past). The NYC subway system on its elevated sections used to use alcohol cars to spray the third rail in order to prevent it from icing. Perhaps Budd Metropolitans are not as tough as MP54s? Maybe WMATA's robot motormen can't operate trains in a snowstorm? (because PATCO's computers can)

As for systems powered by overhead wires, they also ice up. One trick to de-ice the wires is to have a two-pantograph-equipped locomotive raise both pantographs and have the forward pantograph act as an ice scraper. Apparently they were somewhat unaware of this over in Europe, whose overhead-powered systems fell prey to snowstorms and ice storms that US railroads would have continued to operate in.

Also, I don't think interurbans from the pre-depression era are an example we should be following today. The third-rail on the CA&E was a big safety hazard for the railroad. You have to keep in mind that interurbans were built with cheap capital costs in mind which made third rail very attractive

Third rail is not cheaper than overhead wire. And the third rail on interurbans was no "safety hazard", otherwise it would have been replaced quite rapidly.

What sources did you use in your research?

[frischee112]

We're getting off topic. Which is better in your opinion?

[trainmaster611]

Like I said, this is mostly stuff that I'm remembering that I read but I can't remember where I got them except for the interurban safety hazards which came from the book The Electric Interurban Railways in America. But frankly, if you're insisting that I find my sources, I ask you to do the same. Otherwise, we might as well be pulling facts out of our ass.

Now if you want a citation that overhead is more expensive than third rail, I'll cite this study of the Roosevelt Boulevard Subway. On page 8, the cost for third rail is listed as $70 million while overhead is $80 million. I don't know what the context for that number is (like if it's the total construction costs per mile or anything like that). Assuming that this is true, this answers a lot of questions as to why rail agencies don't use overhead wire more often.

I suggest we start finding more sources before we progress this discussion any further to qualify our statements. I'll be looking for more sources myself.

[mtuandrew]

We're getting off topic. Which is better in your opinion?

Moderator's Note: I think the responses so far have given a fair look at both third rail and overhead. Also, in response to trainmaster611's post this morning, this is a separate topic from whether EMUs or DMUs are superior. However, I will be asking Jeff Smith to take a look at the topic later on.

Hopefully all the forum members have had a happy holiday season, and for those who celebrate, a merry Christmas.

[stevegaarder]

One advantage of overhead wires is that they can handle higher voltages; you can't do much more than 1000 volts on a third rail without getting a lot of problems with arcing - it's just too close to the ground. The higher voltage allows delivering more power and reduces the size of the conductors needed. Both of these are more important for mainline railroads, not so much for transit; thus, mainlines usually use overhead while a lot of transit uses 3rd rail.

[trainmaster611]

Like I said, this is mostly stuff that I'm remembering that I read but I can't remember where I got them except for the interurban safety hazards which came from the book The Electric Interurban Railways in America. But frankly, if you're insisting that I find my sources, I ask you to do the same. Otherwise, we might as well be pulling facts out of our ass.

Now if you want a citation that overhead is more expensive than third rail, I'll cite this study of the Roosevelt Boulevard Subway. On page 8, the cost for third rail is listed as $70 million while overhead is $80 million. I don't know what the context for that number is (like if it's the total construction costs per mile or anything like that). Assuming that this is true, this answers a lot of questions as to why rail agencies don't use overhead wire more often.

I suggest we start finding more sources before we progress this discussion any further to qualify our statements. I'll be looking for more sources myself.

Doh! I just realized I left the link out.

http://felttip.com/svmetro/projects/roo ... -costs.pdf

[amtrakowitz]

A study from ten years ago of a subway for Philly that was never built?

[trainmaster611]

How does this make it any less valid? The economics of the technology are the same today as they were 10 years ago.