Maybe this is K.P. Harrier’s invisible train on the move?
This morning, we’re dealing with a big ice storm in our area. I had to take a different route for part of my drive to work, due to ice. As I passed near a crossing at the edge of an industrial area, the crossing lights were on, but no train.
I’ve read where signals and such are passed through a circuit made of of the rails. If you have an inch of ice on everything, doesn’t that mess up a lot of electrical stuff on a railroad?
the ice itself wont cause the problem, but ive seen where the road salt and water lay in the road bed of the crossing and as a big truck or bus would cross over it the weight of the vehicle would mash the rails down into the water/salt mixture and cause the lights of a crossing to come on.
wabash1’s explanation makes a lot of sense to me. Ice from the sky is pretty pure water and as such is not very conductive = high resistance to electric current. But sea water with the salt in it is from 100 to 10,000 times more conductive = less resistance, than drinking quality water. As a most graphic though unpleasant illustration of this principle - I’ve read that the electrode pads on electric chairs were soaked in salt water to assure good conductivity of the current to the condemned. And de-ionized water - which may be closer to rainwater in quality - can even be from 10 to 100 times less conductive than drinking water. See, for instance, the data in the table about halfway down this web page -
http://en.wikipedia.org/wiki/Electrical_conductivity
With some older crossing signal installations, particularly in slower speed, non-block-signal territories, the approach circuit in advance of the crossing has an integrity feature built in. The integrity feature involves continuously passing a small amount of electric current through each rail in advance of the crossing. If this current is interrupted for any reason such as a broken bond wire, a broken rail, or a bond from the feeder cable becomes unattached from the rail, the system is designed to “fail safe,” i.e., the crossing lights and gates become activated.
Maybe, Murphy, what you saw was the result of a break in the track circuit causing the lights to start flashing.
Is there anything related to an ice storm, that would cause a break in the circuit? The street is near a hospital, so it receives a lot of salt in snow and ice storms.
Cold weather can cause a pull-apart, and they don’t seem to be real predictable.
Given the conditions you mention, I suspect the salt is the culprit at that particular location. I’ve heard that road salt and the way it changes the base resistance in the track circuit tend to give signal maintainers headaches.
According to Wikipedia, salt water is much more conductive than fresh water. They show the conductivity of sea water, and I’m sure the way the roads are salted in Michigan makes it even more conductive.
Around here, the local crossing signal constantly gets activated multiple times each winter when the snowplows are out. I’ve even seen them activate it before. The way the circuit’s set up here (and the way the crossing sits doesn’t help), that plow reaches both rails, shorting it like a train axle would, tripping the signal.
Not being a ‘signals’ guy, this is mostly speculation, but a couple of far-out possibilities are -
Ice brought down wires- either the RR’s that lead to the crossing’s controls - or some other utility’s that bridged across/ shunted the rails;
A thickness of ice build-up on and outside of the rail, was forced down and out by the locomotive and car wheels, breaking off a jumper/ bond wire at a rail joint that is of the kind that are spot-welded onto the outside of the head of the rail - as opposed to those that are welded into the web;
Ice accumulated on the gate arm enough to overcome the counterweight and force/ drag it down ?
I’m more inclined to believe the ice-water-salt mixture in the vicinity of the grade crossings as the explanation, though.
The crossing at Main Street, here, was famous, or maybe infamous, for activating when it rained. The crossing is at the bottom of hill, and the water runs down Main and across the crossing. NS has since altered the circuit so this no longer happens.
On another note…I have seen many occasions where ice packed in the flangeways or a plow berm has derailed cars. There is a standing order when working the Piers or Food Center to take a locomotive across a crossing first to break up the ice, and plow berms.
Nick
In the “learn something every day” category, I had no idea that ice, snow, or rain water was not very conductive by itself. Must have been an awful lot of some contamination in it then when I worked for NYC–>PC years ago. Signal maintainers didn’t bother going to bed on rainy or snowy nights; it would have been a waste of time because they were most certainly going to be called out.
Grade crossings were most likely to short out and give false indications of a train approaching. I always thought that was because there was invariably more dirt in the ballast that prevented good drainage. Must have been a lot of conductive junk (road salt and ???) in that dirt.
Signals at certain CPs were notorious for having problems in bad weather. Some maintainers wouldn’t even bother going home on a stormy night; they would just go to their best-known trouble spot and wait for a failure there (or a call from somewhere else).
I’ll jump in here, seein’s how signals is my day job(nights n weekends too, frequently). PDN raises some valid points, and not that far out either, as I have seen all 3 happen at one time or another. I would agree with his evaluation in this case however, that the crossing activation was likely caused by salt in the island circuit.
The city plows will lift the blade a bit when going over the rails–leaves a hump of snow/ice/slush near the crossing–so they dump a little extra salt there to help break it up–and that can play havoc with the island circuit. Slush+salt+rain+poor ballast conditions= gates down.
Not being a ‘signals’ guy, this is mostly speculation, but a couple of far-out possibilities are -
Ice brought down wires- either the RR’s that lead to the crossing’s controls - or some other utility’s that bridged across/ shunted the rails; Yup, seen it…
A thickness of ice build-up on and outside of the rail, was forced down and out by the locomotive and car wheels, breaking off a jumper/ bond wire at a rail joint that is of the kind that are spot-welded onto the outside of the head of the rail - as opposed to those that are welded into the web; Yes, ice will build up and break off bond wires. Rails heat up in the sun, enough to melt the snow then re-freeze at night into a solid mass. Bond wires and track connection wires frozen in this mass are subject to pumping forces from trains and lateral forces from rails contracting/expanding.
Ice accumulated on the gate arm enough to overcome the counterweight and force/ drag it down ? Well it would take
In Council Bluffs, Iowa, just a short ways west of the Rails West Museum housed in the old joint Rock Island / Milwaukee Road depot building, a north-south street crosses a railroad track. Along the curb in advance of this crossing the city has posted a small ceramic metal sign, one which reads “NO SALT.”
The sign probably serves as a reminder to the snowplow trucks not to dump any salt at the crossing because it might interfere with the railroad’s signalling systems.
[:-,] After reviewing all of the above, seems like this is a classic application of ‘Murphy’s Law’ . . .
[Sorry, I couldn’t resist. [swg] ]
Ice is bad in the crossing, especially if you are shoving cars. A crew on our raialroad was shoving loaded tanks cars across a small paved crossing when the front set of trucks on the first tank derailed due to ice.
The solution: run the lococmotive over the crossing first to break up the ice. This must be done with care, and at walking speed.
One of the first derailments I had a hand in investigating in the mid-1970’s was of this type, but with far more tragic results. The lead car was an empty gondola, and late one winter night when when it encountered the mud and ice between the rails at an in-plant grade crossing on a fairly sharp curve, it derailed and turned over, crushing and killing the trainman that was riding the lead end. This happened in a quarry, which is why the mud build-up at the track occurred and wasn’t removed promptly.
I’m curious about the snow plow “shorting” the track circuit. Maybe they activated the vibration detectors? On the NYS&W kids used to bang on the rails to activate the crossing gates in the middle of town.
Oh, and speaking of the NYS&W, they put not one but two locomotives on the ground in one winter by running over ice at crossings.
Vibration detectors?
RWM
I was wondering about that one, too.
Not uncommon. This may be the all-time champ, though, or at least a contender:
So you wanted an SW1200 for Christmas
Trains, December 1987 page 39
switcher derailed, in driveway of house
( ACCIDENT, CNR, FRONTISPIECE, “INGLES, J. DAVID”, TRN )
The house had to be close to the tracks, but still - that big black-and-red switcher dwarfged the ranch or Cape-Cod style house, and looked about like it had just been parked in the driveway !