Broken Rails

How are broken rails (like the one last night by the East River tunnel) detected? Where typically on the rail do they break? What causes them to fail?

when rail breaks, it interrupts the signal continuity so signals will go red.

That's one of the ways, a break causing a circuit to go out which either kills the code (brings the train to restricted speed and then the engineer may see it better as the train crawls over the circuit). Another is an engineer seeing it on an adjacent track. All tracks are inspected by track walkers also, and track cars designed for that may pick up a flaw which isn't visible to the eye, such as the SRS or TC 82. There are many causes, but the biggest culprit is usually temperature. If we have a big temperature swing, the rail either expands or contracts. Sometimes you can compensate by having expansion joints but when you have numerous switches, insulated joints, etc. you can't always compensate for expansion. Also, getting pounded frequently by trains doesn't help. There's some more detailed posts if you do a search back in the forum's posts.

Many times a broken rail is reported by an astute engineer who either sees it, hears it or feels it when it's run over. The report is followed up with an inspection. Often the rail is not broken all the way through and only a portion of the rail head is broken off. In that case, signal indication would not be lost.

You'd be surprised ... if you drive across a broken rail (or loose joint), you can clearly hear and feel it ... esp. if you're tracking inspecting old-school-style in a Fairmont speeder, but also quite easily if you're in a hirail.

It's kinda like this .... ka-tink ka-tink ka-tink ka-tink ka-CLUNK ka-tink ka-tink ka-tink ka-tink ... it's a noticeably different sound.

On welded rail it would be even more apparent since there are no joints ... it's like ... whirrrrrrrrrrrrrr BAM! whirrrrrrrrrr ... a very sit bolt-upright "WTF was THAT" moment.

Those smaller vehicles, you really get to experience track geometry firsthand.

krispy wrote: a break causing a circuit to go out which either kills the code (brings the train to restricted speed and then the engineer may see it better as the train crawls over the circuit).

Unfortunately, this particular warning of a broken rail is not available in unsignalled manual block territory east of Ronkonkoma and east of Speonk.

I believe the crossing gate system also provides notice of a broken rail. If There is an interruption in the circuit near a crossing the gates are activated, if the dispatcher notices a crossing activated without a train nearby that could be an indication of a problem.
I've noticed a few broken rails out east that were identified fairly quickly without any trains nearby so this makes me believe the crossing gate system also provides some warning.