Hi everyone, would anyone know what “time locking” is and was this used on mainline passing sidings in CTC terriotory (durring the early to mid 50’s) to estimate when the siding was clear (once a train had left the siding) for the CTC operator to chage the turnout and signals? Is this correct??
I can tell you that operators NEVER estimate that a train or vehicle is clear… the consequences of getting it wrong are too expensive. If you don’t KNOW that it’s clear you find out.
I would guess that it’s the same as one of the following in UK practice.
- Some tower operated equipment had either a time out or a wind out to release the equipment if it was set for a purpose but the job cancelled. One example was gated level crossings with drop barriers. If the barriers were down and the protecting signal cleared but then the train didn’t run through (maybe it stopped extra long or broke down short of the crossing) then the signal would be put back to red but the barriers could not be lifted until the time out had run its time. this tended to make road users really happy. A wind out was the clockwork equivalent of an electric time out… it was necessary to wind the release 100 times clockwise to get the equipment to release.
- Alternatively it may have been similar to “Approach Control”. this usually occured where a diverging route took off from a very fast main through a sharp curve with a severe speed restriction. In order to make certain that trains didn’t fly round the curve and leave the track the protecting signal could be cleared by the tower but would not give a proceed indication until either the train approaching had been detected to be doing less than a specified speed or the train approaching had been detected to be at a stand for a specified time. If the train approached to fast it would automatically be held for the “at a stand” time. This did not prevent SPADs (Signal Passed at Danger) because there are only two things that stop trains… friction between the wheels and brakes combined with friction between the wheel and rail or something more big and solid than the train getting in its path. Engineers and signals do not stop trains… not even where automatic train control systems are in use. These three work to protect trains from hazards and to manage their spe
I once watched an IC crew near Kankakee, Illinois switch a siding. After they pulled in realligned the switch for the main and spotted the car they pulled back up to the swtch and detrained. I asked them what they were waiting for and they said the switch had a timer on it and they couldn’t open it for fifteen minutes. I suspect that the logic is to be sure that all circuits have cleared and rapid realligning of the switch points may have been interpreted by the dispatcher as a faulty circuit. In reality they could probably have resumed their journey in under a couple of minutes but for safety fifteen was the magic number. I can imagine a dispatcher seeing a light turn from one route to another several times in a short span and calling out the signal maintainer for a fix not realzing it was a crew doing their job.
Not sure exactly of your question, but “time locking” in traffic control system (CTC) vernacular is an interlocking safety measure. Upon cancellation of controlled signal by the dispatcher, the interlocking logic will allow NO CONFLICTING route to cleared until a prescribed amont of time has “run.” The amount of time is typically determined by a worst-case running time for train from the approach signal to the interlocking on the route previously cleared, and thus would vary by location. I’ve seen the “time element relay” (or its solid-state equivalent) configured anywhere from 240 to 600 seconds. When the signal is slotted off normally (by passage of a train through the OS), the time element relay is not activated.
ndbprr appears to be describing the operation of an electric lock. Depending on device (US&S, GRS, etc.), when you want to leave the siding, you operate a lever on the lock which knocks down the track circuit. The lock will “run” a prescribed amount of time to ensure that any train already by the last signal protecting the switch has time to get to the switch (and thus be observed by the train crew wishing to come out). Only after the time has run will the switch be unlocked and operable. To enter a siding at an EL location, the train typically has to pull up very close to the lock where a short audio-freq track circuit detects the train’s presence on the main track and allows the switch to be unlocked without running time.
Hope this helps.
Regards,
Greg
Running ‘time’ is a normal part of an interlocking - Here is an example:
The operator controlling the interlocking lines a route so that a train is routed straight through on the main track. He then realizes that he needs to put the train in the siding for a ‘meet’. He ‘knocks down’ the clear signal and wants to align the turnout for the siding. He will have to run a ‘timer’(or it can run automatically) before he can throw the turnout to the siding(this can take 5-6 minutes). The reason for this is it is possible that the train has already gone by the ‘distant’ signal and saw a ‘clear’ and is moving at track speed expecting a clear home signal at the interlocking. If the control operator could change the turnout in between that time, the train would be approaching the switch at maybe 70 mph, and be routed through a 25 mph turnout. The chance of a derailment is quite high! The length if a ‘timer’ is proportional to the speed of approaching trains.
Jim
Didn’t I say that ? [;)]
[:D]