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Thread: Cruious about crossings (??)

  1. #1
    Join Date
    Nov 1999
    Location
    Chicago, IL.
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    387

    Default Cruious about crossings (??)

    It is claimed that there are more railroad crossings per capita in Des Plaines, Illinois (a suburb of Chicago that borders the northern periphery of O'Hare airport)than any other town in the U.S. Since I work there, it's not unusual that I end up waiting for a train to pass.

    This morning, as I was approaching a crossing, the crossing lights began to flash and gates went down, but no train. Then the gates went back up. As I crossed the track, I looked down the track and saw a train stopped about three freight car lengths from the crossing. So here's my question. Is there a way for the engineer or conductor to activate/deactivate the crossing gates manually via remote control from the cab for those instances where a train has to stop short and wait for a long time before resuming?

    Another related question is, how does the crossig gate sense the approach and departure of the train. Is it that the wheels of the train complete a circuit between the two rails? While that seems too simple an explanation, I'm at a loss as to come up with an alternative hypothesis.

    Any information which would help illuminate my understanding of either or both of my questions would be most appreciated.

    TIA,

  2. #2
    Join Date
    Nov 1999
    Location
    Portage, Wisconsin, USA.
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    307

    Default RE: Cruious about crossings (??)

    Usually the crossings will time out after a train sits on the circut for an certain period of time.
    John 3:16
    Locomotive Engineer
    Canadian Pacific Railway
    Portage, Wisconsin

  3. #3
    Join Date
    Nov 1999
    Location
    Missouri
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    Default RE: Cruious about crossings (??)

    Howdee,

    What you saw was most likely a SAFETRAN motion sensing system.

    This system is common among most railroads now.

    How it works...

    It sends a radio carrier (radio signal) down the rails to a tuned "shunt" at a cetain frequency. When a train crosses that "shunt" , a circuit reads how fast the signal is "shortened" and determines the speed of the train at the crossing contol cabinent.

    Once this speed is determined by the processesor, the warning system at the crossing will activate to give an almost perfect 20-25 seconds of warning time at the crossing (depending how it is set up).

    Now, if the train is stopping within that circuit, once the system has detected no movement, it will clear the crossing signal system.

    One thing to note on that, if a train stops on the "island" circuit (the section of track that occupies the road crossing and 20-30 feet each side of that crossing) then the gates and lights stay active until the train has cleared the island circuit.

    One last thing to note..you can have many crossings set up within each other's trainsmitting range, as long as each crossing is at a different frequency, related to it's own crossing processor.

    That's why when your around a spot where many crossings are close together, each crossing protection system still operate independently from the other, unless they are linked together.

    ..a far cry from the old DC and AC(rusty rail) circuits I learned on.

    (EDIT) spelling
    GM&O SIMULATIONS
    www.mstsgmo.com

  4. #4
    Join Date
    Nov 1999
    Location
    Milepost 8.3, BNSF Omaha Sub.
    Posts
    539

    Default RE: Cruious about crossings (??)

    I recall a few years ago a problem with a crossing that is about 200 yards off the end of the runway of a major military airbase. Regular missions were flown out of this base daily.
    Very often, but not always, when one of these flights would take off to the south and almost right over the crossing in question, the lights would start flashing and the gates would come down, even when there were no trains within 10 miles either way. Usually the gates would time out and open after a short period, other times they'd stay down indefinitely and the maintainers had to be called out. I don't know exactly how the problem was solved, or if the cause was ever 'officially' linked to activity at or from the airbase. Interestingly, in this same time frame, there were many, many reports from residents in the area of automatic garage doors opening all by themselves. This too was unofficially said to be a product of signals transmitted from the flights out of the base.

    Just call me Mulder. :)


  5. #5
    Join Date
    Apr 2003
    Location
    Stony Plain, AB, CANADA
    Posts
    829

    Default RE: Cruious about crossings (??)

    >the airbase. Interestingly, in this same time frame, there
    >were many, many reports from residents in the area of
    >automatic garage doors opening all by themselves. This too
    >was unofficially said to be a product of signals transmitted
    >from the flights out of the base.

    The older garage door openers were a lot easier to trigger. I know of an instance where a garage door kept opening for no aparent reason. Then one day a police car was in front of the house and as soon as the cop started talking on his radio, the garage door opened. Seems the cop radios were sending out a frequency that was close enough to fool the door mechanism. Problem solved. Case closed. :)

    Cheers,


    Gary Cameron
    Grande Prairie "The last civilized stop before Alaska," AB
    Canada

  6. #6
    Join Date
    Jun 2004
    Location
    Toronto, Canada.
    Posts
    687

    Default RE: Cruious about crossings (??)

    >One thing to note on that, if a train stops on the "island" circuit >(the section of track that occupies the road crossing and 20-30 feet >each side of that crossing) then the gates and lights stay active >until the train has cleared the island circuit.

    To add to that Paul when a train is stopped on the island circuit the bell stops while the lights and gates stay active till the train moves to activate the bell again.

    Also there is an electrical circuit that runs on the rails itself but the voltage depends on each railroad last I heard CP had there voltage at 12VDC but there is also polarity between the rails too....meaning that one rail is positive and the other rail is negative and when passing by every insulated joint the polarity reverses so the one rail is negative and the other rail is positive. And when a train passes over that insulated joint it trips the circuit and the polarity reverses causing the crossing to activate and that most crossings have a timing circuit to time out the crossing whenever there is no movement because the train is stopped and I think all railway crossings time out after about 20 seconds of activation in order to stop activating.

    But now a days they have these new ones that send a signal to the rails and determines how fast or slow the train is going in order to give out the max and min times the crossing signals are able to activate before the train comes.

    But you can notice with railway signals too, when ever a train passes over an insulated joint, the signal changes from yellow or green to red meaning that the train has tripped the circuit.

  7. #7
    Join Date
    Nov 1999
    Location
    Missouri
    Posts
    2,916

    Default RE: Cruious about crossings (??)

    Well said.

    The signal circuits for ABS block signals are called "ELECTROCODE"

    When I left the railroad, they had progressed to ELECTROCODE 4. It was a system with a transmitter and receiver at each signal. This transmitted in both directions and received from both, sending a pulse though the rail to the next signal. One pulse ment "occupied".. 2 ment clear. If a train was in the circuit, the opposing signals in the occupied block got no signal at all, which dropped the relay to it's failsafe "stop" occupied position. The signals one block away from the occupied block got a pulse to indicate an "approach" aspect to the occupied blocks.

    Don't know what it is now..this has all changes to digital.

    As for the frequency signal sent down the rail, it was no more than 1/2 a volt to 1 volt, and in the milli-amp range.

    The 12 volt conversions were brought about after DC 10 volt circuits were abolished in allot of main line curcuits (this being the old insulated joints and battery circuits with relays)

    Some DC and AC track curcuits still linger, but most are MOTIONSENSOR equipped now.

    Not sure about the airplane transmitter signals...but anything's possible. I know I had to adjust the transmitters in several SAFETRAN motion sensor systems after a hard rain because the cops would call saying the gates were down with no train, just to come back in a day or two to re-adjust the system back to it's original settings to clear the gates up again because the track and ground dried out.


    GM&O SIMULATIONS
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  8. #8
    Join Date
    Nov 1999
    Location
    Chicago, IL.
    Posts
    387

    Default RE: Cruious about crossings (??)

    Thank you all for the great discussion. I feel I have a much better understanding of how crossing signals work. Far more sophisticated than in the "good 'ole days."

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