Track work question

[marnegator]

Good day! Decided to end my forum-lurking days. . .
I've taken an interest in the track bed replacements that have occurred at Wall St for the 2,3 trains and the 42nd St (BMT) uptown express track. I'm not sure when Wall Street had its downtown track bed replaced - it looks pretty new - but I enjoyed watching the 42nd St construction just some weeks ago and something hit me: why aren't the tracks all welded? 42nd St had everything ripped out and then had jointed rail put in place? Wall St seemed in better shape but it did have a couple of joints. The jointed rail at Wall St also mystified me: where the rail was jointed, it had what appeared to be a "spacer" between the rails and heavily bolted together. Anyway, I bring this up because I thought it was the intent to have the subway fully CWR; it seems wasteful to lay jointed rail for future replacement when they could do it all at once.
I apologize about my lack of research

*edited for stupidity*

[RearOfSignal]

One reason is the length of signal blocks. Joints are needed to separate the blocks electrically. In areas where there are curves or home signals, GT or ST signals or when approaching the end of track shorter blocks are necessary to control train movements, thus more joints.

[marnegator]

Ahh. . . that would make some sense! Sorry about the late thanks, lest I be taken for ungrateful!
On a side note, when the subway is fully CBTC - in the next thousand or so years - would there still be a need for joints? Or would they keep the old system as a backup and thus need a few remaining joints? Thanks in advance!

[RearOfSignal]

By the time CBTC is installed system wide it will be out of date. So who knows?

[Gerry6309]

In addition to signalling, the temperature swings in the subway are a factor. There are many curves with no room for heat kinks, thus frequent joints. Where there are long runs of straight rail, welded rail is the rule. Insulated joints are much larger than regular joints, and are often painted red or orange.

[marnegator]

I had no idea that heat kinks would be a factor, especially inside of a tunnel. Even without direct sunlight, the track in the tunnels are that greatly affected?
If you will all bear with me, I would like to ask a further question on the track bed work that goes on in the subway, specifically ties. Why do they continue with wooden ties? It's integrated with the new concrete track bed, but isn't the wood going to be the bit with the shortest lifespan? I also notice that in the few released pictures of the under-construction South Ferry Terminal show tracks resting on concrete ties. Unless I misjudged wood for concrete in the rather low-res pictures, why the discrepancy between one section of track and another? All I can figure is the relative cost of the materials. Thanks in advance.

[gjk1716]

I have been in NYC Transit's Track Department for 13 years. When I was still working in the subway, I noticed a section of concrete tie blocks that had cracked under the stress. With the constant traffic and sharp curves, these tracks take a lot of abuse. In addition, much of the track maintenance work is still done by hand, because of the limited space and 24-hour service. It would seem difficult to install concrete ties without heavy equipment, except during a major construction project, like the one you mentioned. I have seen tie blocks made of composite materials, but not any on mainline track. NYC Transit is constantly experimenting with different materials. I have to take a class at PS 248 (our training center) in late July, so I will try to remember to ask about concrete vs. wood ties. There's no guarantee I will get the right answer, though .

[gjk1716]

I just completed my two day Track Inspection refresher course at PS 248. I did not have an opportunity to ask why NYCT still uses wooden ties, however, I noticed that they are installing panels of 115 lb. rail with concrete ties along the northbound N-line near New Utrecht Avenue. That type of track seems best in ballast. It could be too rigid for use in the subway.

-G-

[marnegator]

Thanks for remembering! No problem about the question, most of my curiosity having been satisfied. Thanks again.