Train tracks don't grow on trees, son

July 24, 2006 11:17 AM

Why are they watering the railroad tracks?

I live in Portland, OR. I was crossing the Steel Bridge on my bike this morning, and there were two spots on the train track part of the lower deck that had sprinklers running on them, watering the tracks.

While the water felt good on this 70-degree morning, I can't help but wonder - why water the tracks? Is it so that the track doesn't buckle or bend in the heat Portland's had recently, or is there something else going on? If it's to prevent the track from buckling, why only water two spots?

posted by pdb to Travel & Transportation (5 answers total)

I bet they were watering the area at the two ends of the lift section, weren't they? That's a place where the track needs to line up but adjacent sections of track aren't physically connected, which means it's particularly vulnerable to heat-related buckling, or just to movement due to thermal expansion.

For those not familiar with it, the Steel Bridge is a vertical-lift bridge. It has a train track on the lower section and a roadbed on the top, but there are also rails on the top which are used by the MAX light rail system.

I suspect they were concerned over thermal expansion of the free section of track that the MAX was using.
posted by Steven C. Den Beste at 11:27 AM on July 24, 2006

Response by poster: I bet they were watering the area at the two ends of the lift section, weren't they?

They were indeed, now that I think about it.
posted by pdb at 11:31 AM on July 24, 2006

Boston and Toronto also water the tracks to stop wheel squeal. This is most often used on curved sections of track.
posted by Raybun at 12:15 PM on July 24, 2006

Right, I'm going outside to the curved bit of railway track outside my flat with my watering can*. I've been woken up at 5am for the past two weeks by a squeaky train during this heatwave.

* because hosepipes are banned at the moment
posted by randomination at 3:27 PM on July 24, 2006

I'm not familiar with that bridge, but do the rails lie on wooden sleepers? Braking to a stop heats up the undercarriage of a train tremendously (all that kinetic energy converted to heat), and if a train remains stationary in one spot for long enough, it runs the risk of igniting whatever it's stopped on top of. Because of this, trains are often forbidden from stopping for extended periods in unsafe areas unless it's an emergency. Soaking the structure with water might be a precaution against such fires.
posted by randomstriker at 6:16 PM on July 24, 2006 [1 favorite]