What are these "pipe arrows" at railroad crossings?
August 11, 2015 10:40 AM
I've seen these since I was young and always wondered what they are. Example 1. Example 2 and another angle. The pictures are from Google and aren't the best, but you can see what I mean.
They are made of iron or steel pipe and are shaped like arrows pointing up. They were painted yellow (already fading) when I was a kid, but none that I've seen have been painted or maintained in years. I don't believe they are meant to move or be moved in any way.
I assume these are used as some sort of markers but for what and who? For the train engineer? Train ground crew? Pedestrians or motorists?
These seem to only still exist at railroad crossings that have not been built or rebuilt in the last 30 years or so. There is a line near my house where the tracks and signage were pulled out years ago and these are still present in some places even though you'd never know there was a rail-bed there if you hadn't seen it when it was active. I've seen these in the suburban Twin Cities, Minnesota area on Union Pacific lines. There are none of these at the nearby large UP rail yard on any line or siding - but that's all been rebuilt many times over the years.
They are made of iron or steel pipe and are shaped like arrows pointing up. They were painted yellow (already fading) when I was a kid, but none that I've seen have been painted or maintained in years. I don't believe they are meant to move or be moved in any way.
I assume these are used as some sort of markers but for what and who? For the train engineer? Train ground crew? Pedestrians or motorists?
These seem to only still exist at railroad crossings that have not been built or rebuilt in the last 30 years or so. There is a line near my house where the tracks and signage were pulled out years ago and these are still present in some places even though you'd never know there was a rail-bed there if you hadn't seen it when it was active. I've seen these in the suburban Twin Cities, Minnesota area on Union Pacific lines. There are none of these at the nearby large UP rail yard on any line or siding - but that's all been rebuilt many times over the years.
You're thinking of a pipeline casing vent marker (scroll down for an image)? This article talks a little bit about why they are there.
posted by Joe Schlabotnik at 11:23 AM on August 11, 2015
posted by Joe Schlabotnik at 11:23 AM on August 11, 2015
Here is a better picture of one. If you explore that website, there are plenty of crossing pictures without this item. And of course many crossings don't have a pipeline under them. So the casing vent marker answer makes sense. If I understand the explanation in the article correctly, what is being vented is the air inside the outer casing through which the pipeline has been laid, since there will be expansion/contraction with temperature changes, etc. The arrow-shaped ones seem to be kind of obsolete.
posted by beagle at 11:36 AM on August 11, 2015
posted by beagle at 11:36 AM on August 11, 2015
It's just that easy I guess. I tried to look for things relating to gas lines because somehow I suspected that but my Google powers were weak. Then I figured that it probably wasn't gas pipeline related because of the number of them, but I guess there are gas pipelines absolutely everywhere. I would have guessed there'd be fewer, larger lines especially in the middle of nowhere. Unless they actually run under and along the rails and that's why they are or were at every crossing around here.
Thanks!
posted by Clinging to the Wreckage at 11:51 AM on August 11, 2015
Thanks!
posted by Clinging to the Wreckage at 11:51 AM on August 11, 2015
Oil, gas, and other petro pipelines tend to parallel many railroad lines. Also, there are fiber optic lines. I don't know if they require vents, though.
posted by Midnight Skulker at 12:07 PM on August 11, 2015
posted by Midnight Skulker at 12:07 PM on August 11, 2015
This thread is closed to new comments.
posted by the Real Dan at 11:03 AM on August 11, 2015