I found this video about a British school for signalmen. Check out the model of interlocking machines.
https://www.youtube.com/watch?v=ZDFYtMpN-yQ
Jeff
Question on a 2 MT line interlocking
At the interlocking track 2 has turnouts A to track 1 then turnouts B from track 1 to track 2. track 2 is out of serice between A and B but not interferring with A or B. Can a train appproaching A be routed to track 1 then back to track 2 on B ? I can imagine the possibilities on the NEC 4 tracks with a train on track 4 going to track1 then back to tracks 2,3, or 4 . Would this be possible at all interlockings or just some ?
Now what would the signal aspects and displays for such moves. Can imagine might different for different RR divisions and whether speed signaling or route signaling is used? Cannot imagine how the signaling on the old B&O CPLs. Balt is this movement possible at AF and once it becomes 4 MT ?
blue streak 1 Cannot imagine how the signaling on the old B&O CPLs.
I believe the appropriate aspect would be either green or amber with the lower center marker lit.
That's based partly on the rules, and partly on observation of operations at Deshler.
Clarifications and extensions welcome.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Jeff wrote earlier in this thread: "An 'automatic' interlocking lines up a route automatically when a train hits the approach circuit. First train gets the light."
How does the automation know which route the train is supposed to take?
Lithonia OperatorHow does the automation know which route the train is supposed to take?
In 'traditional' CTC the route is selected by the dispatcher, and lined for each step "before the train gets there".
Jeff's version is a little more like an automatic version of the north end of the 'Races to the North' in late Victorian England where the two competitors had to 'share' a single track at the end, with the 'first to get there' getting the occupancy. That still involves someone determining routes in either direction through the plant, and then lining things physically according to the "choice" for the train first getting to the limits (and knocking down or choosing an alternate route or hold on the later one). If you are clever you can have a computer do this with speed and efficiency, but if you are wise you will always have a human in attendance on it.
Note the extension of Jeff's idea to a world in which there is proper CBTC and cab signaling with no non-emergency waysides. Each cab display is nearly continually updated (e.g. once every 6 seconds) with advisory display of all other traffic; if there is going to be a 'close call' it can be avoided by predictive logic well ahead of the point that the first train reaches the 'decision point'. The line might be chosen to expedite the 'first' train, or it might give precedence to the modern equivalent of a 'superior' train or class -- for example loaded Z trains over manifests, or trains with crews starting to run foul of hours of service. Incremental adaptation of whatever LEADERlike speed/grade profile is being used then follows to adjust train speed with minimum opportunity cost in order to get everything through the interlocking expeditiously. (Repeat this continuously for all such points across the network -- hence the computers with AI/ES
Lithonia OperatorJeff wrote earlier in this thread: "An 'automatic' interlocking lines up a route automatically when a train hits the approach circuit. First train gets the light." How does the automation know which route the train is supposed to take?
Automatic interlocked railroad crossings at grade contain no turnouts - straight track moves for all routes.
Never too old to have a happy childhood!
In my proposed answer to the very fdifficult deverging-route problem at Shell Interlocking, which I did as an unpaid Klepper-Marshall-King project for my goםd friend Noah Caplin, planner at Metro North, while I was a Metro-North reverse-commuter, entrance-and-exit control, with a computer-system or very complex solid-state relay actual control of switches and signals, will be necessary to minimize delays with the maximum number of same-time parallel movements:
Amtrak had pushed for a simpler and more straight-forward solution: Going west from New Rochell, the four tracks through the station would become six, and each track between the local and express track in each direction would rise and fly-over for the Pwenn. Sta. direction. But this would have required considerable widening of the RoW at the choke point, meaning removal of many homes and business, and streets. East of the station, MN has plenty of land, where there once were a coach yard, rounhouse, and turntable.
Track 5 is the old Harlem River Shuttle siding, not use often now, but still there.
I just stumbled across this discussion, sorry to be late to the party.
I have always been a "tower fan" - back in the 70s there were several towers/cabins which I would spend the day, with permission from the operator. Those days are long gone. The last tower I visited (with permission) was in Springfield, Il - Ridgely Tower...was invited upstairs by the operator...back in 2007 I was in transit to a customer in Western Il, and stopped by. The tower featured Armstrong levers and the associated hardware.
Friendly operator and I could have stayed all shift, but a 1030am appointment got me on the road. The operator indicated (at the time) Ridgely was in no danger of closing as the investment would be over $9 million. He indicated only five towers existed on UP at that time - Lennox Tower in Mitchell, Lake St and Clybourn in Chicago and Avondale Tower in Louisiana and Ridgely.
On April 7, 2010 I again stopped at Ridgely and the operator indicated "30 more days"...new hardware was in place. That was my last visit to Ridgely.
Not sure how many towers are still operating. Here in NW Indiana, I can think of two - Hick on the NS and the bridge at Michigan City on Amtrak Michigan line. Both control bridges.
I am happy these days to find towers still in existance. I know the Marion, Oh tower is operating as a museum. There are a few in Chicago still in operation (correct me if wrong), but there is no way one will be invited into those.
There is a very nice tower at Berea, Oh still standing...in fact I monitor the Berea webcam (and scanner) and the tower is on my other computer screen as we speak.
The most knowledgeable expert on towers is Jon Roma. Google him and you will find a wealth of information on his web site.
Towers were great places to visit, as long as one was invited and stayed out of the way. During my travels in the 1990s, I would come across abandoned towers in Illinois (Momence, and Tuscola come to mind) and I would enter the towers and help myself to old "Train Movement" records...usually bundled by month.
Ed
Lithonia Operator Jeff wrote earlier in this thread: "An 'automatic' interlocking lines up a route automatically when a train hits the approach circuit. First train gets the light." How does the automation know which route the train is supposed to take?
Most "automatic" interlockings are protecting diamond crossings - there are no complicated routes, just preventing both railways from occupying it at the same time.
There is an "approach" circuit with a timer, when a train occupies the approach block it triggers the interlocking and clears the signal. A train approaching on the other railroad will NOT get a clear signal because the first railroad hit it first.
Chris van der Heide
My Algoma Central Railway Modeling Blog
blue streak 1 Question on a 2 MT line interlocking At the interlocking track 2 has turnouts A to track 1 then turnouts B from track 1 to track 2. track 2 is out of serice between A and B but not interferring with A or B. Can a train appproaching A be routed to track 1 then back to track 2 on B ? I can imagine the possibilities on the NEC 4 tracks with a train on track 4 going to track1 then back to tracks 2,3, or 4 . Would this be possible at all interlockings or just some ? Now what would the signal aspects and displays for such moves. Can imagine might different for different RR divisions and whether speed signaling or route signaling is used? Cannot imagine how the signaling on the old B&O CPLs. Balt is this movement possible at AF and once it becomes 4 MT ?
Specific indications depend on the RR, since RRs have different styles of signals and sets of indications/signal rules.
However, there is a general logic to how things work that can help determine what the answer is.
Basically there are two general types of signal systems: Route signalling, and Speed signalling.
Route signalling basically gives simple "clear" or "diverging" aspects, and the crew must figure out their speed based on TT speed restrictions at that point. Speed signalling actually specifies the speed restrictions for the turnouts in the indications.
Back to the question.
If you go straight on one track, you can get a "clear" indication.
If you cross from one track to another, you'll get a "diverging" (route) indication, or a reduced speed (limited (45), medium (30), or slow (15) depending on the design rating of the turnouts.
If you cross from one track and back to the first, you're still going through those switches so you'll basically get the same indication as above.
If the interlocking has more than two tracks, it's really the same. Diverging or limited/medium/slow indications based on the switches you're going through, based on the most restricted set of turnouts you're using. If all the turnouts are identical, you'll pretty much get the same signal indication to any track other than straight through.
B&O's CPL signals are speed signals - you figure out what speeds and indications can be displayed in your situation(s) (eg. "Medium Clear", "Slow Approach", etc. etc.) then use the signal charts from whatever system you want to use to determine what those aspects look like.
https://www.railroadsignals.us/signals/cpl/CPLaspects.jpg
cv_acr Lithonia Operator Jeff wrote earlier in this thread: "An 'automatic' interlocking lines up a route automatically when a train hits the approach circuit. First train gets the light." How does the automation know which route the train is supposed to take? Most "automatic" interlockings are protecting diamond crossings - there are no complicated routes, just preventing both railways from occupying it at the same time. There is an "approach" circuit with a timer, when a train occupies the approach block it triggers the interlocking and clears the signal. A train approaching on the other railroad will NOT get a clear signal because the first railroad hit it first.
Thanks, Chris.
I wouldn't have thought a simple diamond would ever be referred to as an interlocking.
I guess I don't really understand the meaning "interlocking," in the broadest sense. I thought an interlocking always involved at least two switches (and often many more), and provided an option (or options) to change routes. And I thought that the switches were connected in a way that when one route was aligned, it was physically impossible for any conflicting route to be aligned. And that the signaling would also support only one route, and forbid all conflicts.
So what is the most basic definition of a railroad interlocking? I never dreamed that a simple diamond would qualify.
Lithonia OperatorI wouldn't have thought a simple diamond would ever be referred to as an interlocking.
As I describe below, one of the interlockings I was at was at Dunrieth IN where a single track NKP branch line crossed the double track PCC&StL (PRR) main line to St Louis. No switches. just two diamonds and signals. I believe there were derails on the NKP. But that was over sixty years ago.
Lithonia Operator I wouldn't have thought a simple diamond would ever be referred to as an interlocking. I guess I don't really understand the meaning "interlocking," in the broadest sense. I thought an interlocking always involved at least two switches (and often many more), and provided an option (or options) to change routes. And I thought that the switches were connected in a way that when one route was aligned, it was physically impossible for any conflicting route to be aligned. And that the signaling would also support only one route, and forbid all conflicts. So what is the most basic definition of a railroad interlocking? I never dreamed that a simple diamond would qualify.
No, an interlocking doesn't actually have to have switches.
It's a set of signals that are "interlocked" together so that conflicting routes cannot be set up.
In the case of a diamond crossing, you cannot allow both routes to use it at the same time, so signals are interlocked so that if a route is cleared in one direction, nothing can be lined on the crossing route.
If an interlocking does include switches, the switches are also interlocked so that
1) signals cannot be cleared when a switch is thrown against the route
2) switches cannot be moved if a route is already cleared over the switch(es)
3) conflicting routes cannot be cleared
If there are no switches 1 and 2 obviously don't apply but 3 certainly still does.
Consider that Brighton Park was not an interlocking until recently. All trains had to make a statutory stop and be flagged or manually signalled across by the watchman.
In 1964 at Montgomery IL on the CB&Q there was a collision between a detouring Rock Island passenger train and a Burlington passenger train. It happened at a manual interlocking which was being modified. During the modification process, it temporarily, under certain conditions, allowed a confilicting route to be lined up. IIRC, this was known and a reminder note left for the operators. The link has some info and pictures of the aftermath.
http://railfan44.blogspot.com/2014/01/major-passenger-train-wreck-montgomery.html
More than a few diamonds had a simple smashboard that swung across one track or the other, no doubt with some time restriction.
Jeff, thanks for posting that link.
Lord, what a horrible accident. The impact relative speed was approx. 59 mph (59 + 0). I wonder what the highest ever relative-speed train collision was. I'm guessing it could be well above 120 mph.
The sound of that Montgomery Tower crash must have been ghastly.
The article says three died, but comments below say four.
BTW, the article states, "An interlocking plant is a location where trains may switch tracks, enter a train yard, or diverge to a different line," and I've always thought it was confined to that.
tree68 More than a few diamonds had a simple smashboard that swung across one track or the other, no doubt with some time restriction.
Those kinds are still around. There's one at Tara IA that protects the UP crossing the CN (ex-IC). It's manually operated, a UP crewmember must swing the gate across the CN. The CN has CTC from Tara eastward to Ft. Dodge, IA, about 8 or 10 miles and I think the UP crossing is within the signalled territory so the gate is probably connected to the CN's signal system.
Some places where two low trafficed lines cross, the diamonds are only protected by a stop sign. Stop, look both ways, blow and go.
blue streak 1 wrote the following post 2 days ago:
"Question on a 2 MT line interlocking
At the interlocking track 2 has turnouts A to track 1 then turnouts B from track 1 to track 2. track 2 is out of serice between A and B but not interferring with A or B. Can a train appproaching A be routed to track 1 then back to track 2 on B ? "
I did that on the P&LE's CTC once. I stopped at a red signal and went to the phone (before radio days). The dispatcher said he was going to loop us around. I said What?? He said one of the crossovers would not return to normal so we would crossover to #1 track and then right back to #2. He could not line a signal for the move so he gave permission by the red signal.
Mark Vinski
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