How long do the rails in a subway last?

January 3, 2006 5:10 PM

TrainFilter: How long do subway rails last? Given the heavy pounding and near constant use that subway rails undergo, how long do they last? Are they simply replaced when I'm not looking?

I ride the Toronto subway a lot. (The question is the same for any city, though.) I always notice how shiny the tops of the rails are, indicating a hell of a lot of heavy use. A subway train rattles over them every couple of minuets, for nearly 20 hours out of every day. It made me wonder, how long can these rails last before they have to be replaced? They have to wear out eventually, right?

The Yonge subway line is over 50 years old. I find it hard to believe that the rails could be the original ones. But, I can't remember a large section of the line ever being closed for an extended period. (Although I may not have noticed, growing up in the suburbs.) Do they replace sections for the few hours a night while the subway is closed?

Pardon the silly curiosity, but it's sort of nagging at me. Feel free to correct any mistaken assumptions!

posted by generichuman to travel & transportation (19 comments total)

Fiance's dad is a former BART engineer, I'll see if I can drag some info out of him, but I believe the rail life time is pretty good, on the order of 30 years. Most commuter subway/trains are actually LRV's which put far less wear in to the rails and far less wear in to the foundation of the rails than you might expect.

From what he was saying when I asked a similar question years and years ago is that most of the rail replacement required is due to abnormal wear due to foundation shift.
posted by iamabot at 5:18 PM on January 3, 2006

In Atlanta, they've recently started redoing some of the work on the rails. It's been thirty years (approximately) since they were put in. (I'm not sure if certain "trouble spots" were fixed in previous years.)
posted by itchie at 5:21 PM on January 3, 2006

NYC plans to spend $117 million this year replacing tracks for New York City Transit, the Long Island Rail Road, and Metro-North Railroad.
posted by nicwolff at 5:22 PM on January 3, 2006

They do have work crews doing repair overnight on the TTC, but I couldn't say for sure whether they're replacing rails. They also do extended repairs on Saturday night / Sunday morning when the subway is closed longer.
posted by jacquilynne at 5:26 PM on January 3, 2006

I saw them replacing tracks in NYC once last summer, deep on a weekend night. They had ripped everything up: track, ties, railbed. They were steamrolling the bed when I went by. Pretty impressive equipment on that job.
posted by armchairsocialist at 5:32 PM on January 3, 2006

Thanks for the answers. It had been bothering me because it seems to be a major project that's done largely invisibly, if at all.
posted by generichuman at 5:34 PM on January 3, 2006

In my search while stuck in the office I stumbled upon this site, which has a ton of information. The overall feel I get is that rail replacement is highly dependent on environmental and operating concerns, there doesn't appear to be a fixed lifespan.
posted by iamabot at 5:38 PM on January 3, 2006

It's more the foundations that fail, not the rails themselves. The wooden ties rot. The foundation erodes. Things start shifting, the rail starts losing its support, and it has to be replaced.

I'm sure there's still 99+% of the original rail left when they're replaced. Modern steel is extremely high quality.

If you'll notice in Toronto, the thing that causes street car tracks to be replaced is failure of the concrete around the rail, not the rail itself.

The Toronto subway closes at night, and I assume most track work is done during the closure period - one section a night, or whatever. The NYC subway does not shut down at night, and often has weekend-long track closures (late Friday evening until early Monday morning) to replace a lengthy section of track.
posted by jellicle at 5:48 PM on January 3, 2006

Consistent with jellicle's description, the Toronto subway had new rail clips throughout the system in the late (very late?) 90's. I thought I heard about new rail at the time too, but I didn't see any evidence of such. With the clips, you could see the new materials laid out along the track ready for installation, and you could see the old materials along the track waiting for disposal.

You have to imagine that the track wears out too. It might get too bumpy long before the track surface gets too thin.
posted by Chuckles at 6:13 PM on January 3, 2006

In the US, rail weight varries from 80-90 lb/yd (pounds/yard) in small yards to 100-110 lb/yd on light duty track and between 130 and 141 lbs on heavy duty track .... Highest price steel rail costs $700 a ton (2000lbs). A 133 pound rail costs $46.55 per yard (0.92 m.).

Wow; if I read that right, it's $88.67 per foot for heavy-duty track. Or $468,000 per mile. Still, it's a lot cheaper than Interstate highway.
posted by rolypolyman at 7:41 PM on January 3, 2006

... on second thought I'm comparing apples and oranges. Track cost doesn't account for grading, sleepers, etc.
posted by rolypolyman at 7:42 PM on January 3, 2006

erm, I got $49.65/yard for 141lb track, which would be $16.55/foot. Am I missing something?
posted by devilsbrigade at 9:23 PM on January 3, 2006

< href="http://www.findarticles.com/p/articles/mi_m0BFW/is_9_100/ai_n6213709">NYCT: 100 years of m/w; after a full century of operation, NYCT has learned lots of valuable lessons in how to keep the New York subway up and running

For the next five years, we're looking to completely reconstruct 22,000 feet a year on the subway
posted by fred_ashmore at 2:25 AM on January 4, 2006

Administrator please hope me. Did not mean to click post. http://www.findarticles.com/p/articles/mi_m0BFW/is_9_100/ai_n6213709
posted by fred_ashmore at 2:27 AM on January 4, 2006

Chuckles writes "It might get too bumpy long before the track surface gets too thin."

Track unevenness is only really a problem where braking occurs.
posted by Mitheral at 5:31 AM on January 4, 2006

While I have no concrete data on the TTC subways, they must get replaced. This is based on my one other TTC datapoint: streetcar tracks. You have no doubt noticed as those have all been replaced over the last few years - King, Queen, Dundas and Bathurst have all been replaced, making my life difficult off and on for several years now. Other have been fixed to, but mercifully I don't have to ride every streetcar in Toronto.

They seem to avoid replacing intersections, presumably because they're very complicated (all those curved tracks) and because shutting intersections would be even worse for vehicular traffic than the normal lane closures.

The underground tracks would get less wear than streetcar tracks because of the lack of sand, salt, etc, wearing into the tracks, but I imagine they wear out just the same.
posted by GuyZero at 6:33 AM on January 4, 2006

Most of the work on the streetcar tracks, though, has nothing to do with the rails. It's the roads around the tracks that have to be replaced and fixed.
posted by jacquilynne at 6:41 AM on January 4, 2006

Well, ok. But they don't just put the old tracks back in - the steel tracks are replaced, which to me seems to indicate that there was something wrong with them. They're expensive enough that I assume the TTC would reuse or recondition them if possible, but they don't, at least not on-site.
posted by GuyZero at 8:16 AM on January 4, 2006

I came across Transit Toronto when googling about this question. No specific answers I don't think, but lots of other great stuff.

Mitheral, why braking and not acceleration? Also, from some of the links here I got the feeling that corners were an issue... Of course on a subway a pretty big percentage of the total track length is subjected to braking/acceleration very frequently... I noticed talk about track grinders in fred_ashmore's link (which is awesome, Thanks!).

On the torpic of fred_ashmore's link, it sounds like all the track in New York has wooden or plastic ties, even in the tunnels. In Toronto the track in tunnels seems to be laid very differently - here is a picture. As I said earlier about the clips, I can remember them changing these steel pads and the clips and bolts that held the steel pads and track down.

GuyZero, I expect that cleaning the old track enough to get new concrete to bond would be impractical, not to mention how hard it would be to pull it out of the ground without ruining it. Also, at $200/ton for scrap steel (I had to look it up, but the link I used is gone now...) they get about 1/3 of the cost of the new track back. So, it really wouldn't make any sense to use the old stuff.

When they re-did the streetcar track along college, if I recall correctly, they would shut down a major intersection for a weekend and work 24hrs/day on it. Some of the details are fuzzy, but I can remember a huge number of workers in a frenzy of activity, and a bunch of cops 'keeping order', all under huge spotlights in the middle of the night. I can remember it moving from one major intersection one weekend to another a week or two later.

Finally, I worked at Centreville for a couple of years and 'fondly' remember packing ballast on the train ride's track with a big steel rod - they called it doing ties. It caused a ton of blisters, but it was kind of cool (now that I don't ever have to do it again).
posted by Chuckles at 9:23 AM on January 4, 2006