Last week I was in Alpine, Texas, which is near the Big Bend Country, for some cycling. Alpine as well as the surrounding area is a great spot for some serious train watching. It is on the Sunset route. In addition to hoisting Amtrak # 1 and 2, as well as numerous UP freight trains, it is a crew change point for both operations.
The UP freight trains, as well as Amtrak’s Sunset Limited, stop just short of a grade crossing immediately to the east of the station, which also houses the UP’s office that is used by the crews to log in and out.
As a train approaches the grade crossing, the bell, warning lights, and crossing gate are activated as if the train is going to run through the crossing. However, it stops short of the crossing for the crew change. After the train stops, just before the crossing, the gate goes up as the bell and lights cease functioning.
After the crew change is complete, the engineer turns on the head and ditch lights and sounds the horn. As the train begins to inch forward the crossing gate, as well as bell and lights, is activated. What causes the crossing warning signals and the gate to activate when the train begins to move?
Also, I observed many UP freight trains with two or three locos on the front and one or two locos on the back. The locos on the back were unoccupied, which means, I assume, that they are being controlled remotely? One of the crew members told me that the rear locomotives are controlled by the crew in the front engine using GPS to transmit the throttle and brake signals. How does this work?
The crossing signals are equipped with predictor circuitry. When the crossing senses that the train is no longer approaching it shuts off. Then when the train again begins to move towards the crossing it turns back on. This type of crossing control is becoming more common, but with thousands of crossings many have older equipment.
No GPS is involved. The locomotives are equipped with the modern version of Locotrol, which is now called Distributed Power, or DPU. With DPU equipment the lead locomotive can control 4-6 remote locomotive consists within his train, each will responded to his movements of the controls just like the locomotives connected by the MU cable. Within the remote consists only one locomotive is being controlled by radio, from that locomotive any coupled to it are being controlled through MU cables. The locomotive Engineer also can directly control remote locomotives through a touch screen on the lead locomotive to operate at different settings to the lead consist. The term for this is called “Putting up the Fence”, while if he has the remote locomotives doing the same as the lead locomotives it is called “Mirror” mode. On another forum a poster showed a video with a CP Intermodal train 11,875 ft long running with 4 locomotives in a 1 + 1 + 1 + 1 configuration. Each locomotive making up a consist by itself. This arrangement makes for very good slack, and braking control.
Thanks for your response. It is very helpful. What happens to the ability to control the remote locomotives when a tunnel, canyon wall, etc. separates the lead locomotives from the remotely controlled locomotive(s)?
That used to be a big problem with earlier versions of Locotrol, newer versions with improved radios and digital signals mitigated the problem quite a bit. but there are still a few problem areas. It is my understanding that the current generation of DPU is good for about 7500 ft. of train. In the case of this train the intermediate remotes repeat the signal going in both directions so that the longest distance the signal needs to travel is much less. That particular train wasn’t that long west of Calgary in the mountains and canyons. It was put together for the run from Calgary to Toronto. Nevertheless CP does use DPU on their shorter but heavier coal trains in the Rocky Mountains and Frazer River canyon.
At the risk of being condescending with a more detailed explanation -
Older grade crossing circuits are based on the track typically being divided into 3 insulated sections, called an ‘island circuit’ configuration. The middle section is usually real short, extending only for a few feet on each side of the crossing itself - but the outer or ‘approach sections’ that start the signal might be several thousand feet long, to provide adequate time for the signal to activate and come down, usually on the order of 20 to 30 seconds or so. The wheels and axles of a train bridging between the opposite rails complete a circuit that ‘shunts’ a relay in the crossing signal equipment cabinet and cause the signals to operate.*
Well i can see where you would think that but know that is not the meaning or the implyed point. In reality a 11.875 ft long or really about anything over 8000ft and the longer the easier. If you put 2-3 unts on the head end and leave town. Now if you take a 7500-9000 mixed train at around 7500-15000 and DPU the thing it be the sweetist runnning train and even if you did like we use to in the days of the southern and run them like slaves now that would be sweet and sorta old school.
The reason being is a long train requires very little train handling put it in notch 8 and drink your coffee wave at Mrs Roosevelt, read make phone calls etc. See i told you we made things look easy, in reality if you see a small train running at track sped that engineer is working his but off. staying on top of his train ,
Hmm - OK, wabash1 - I gotta take it on faith from the man who does it almost every day and knows. [tup]
Reminds me of something similar we had here a while ago, where the bigger or longer it was, the easier the actual operation - kind of contrary to what the uninformed would expect.
I can see where the short train would be kind of like driving a tractor-trailer truck up and down hills - it’s either all on the upgrade, or all on the downgrade, so the speed wants to ‘swing’ radically, so the engineer really has to stay on top of it - on the throttle going up, and on the brakes going down.
Now one of these longer trains might drape over a couple humps and sags of a ‘hogback’ profile at the same time. So, on balance and as a total, it’s not really going up or down much at all.
There’s a ‘puzzler’ that I heard on Car Talk a few years ago about why an 80-car train could get over the road, but a 60-car train with the same locomotive couldn’t. The reason was that the ruling grade was short and about 60 cars long, so that train would stall on it; but the 80-car train always had at least 20 cars on the downgrade at one end or the other of the upgrade segment, which provided enough extra pull to counterbalance some of the 60 cars to enable the locomotive to haul the rest up the grade [or something like that - and I know, a short sharp grade like that can’t be ‘ruling’ for a train like that because it could be run as a ‘momentum’ grade, etc., but that just complicates things here].
I can see that the DP units would make the slack control easier. But what I’m having a hard time understanding is how a long train with all the power up front would be so much easier to control the slack in.
Paul if the slack is in what is doing all the work?? Keep it simple , a easier way of thinking if you had a wagon loaded with stuff to complete the building if your miniture backyard railroad, your wife took off with the pick/up and now you have no way of getting it there, while cussing a car shows up full of high school football players. they offer help so you on the front pulling and the kids behind you ( 5 of them) pushing your loads pretty easy all you do is steer because the work force is behind you. same with dp if the engines are on the rear thats what you use makes the ride up front very nice.
Oh and if you wondered why the highschool foot ball team was doing at your house well they found out you had oreo’s a great looking daughter and most of all you had connections to Mrs Roosevelt.[8D]
Ahh - now I think I see. [;)] Why mess up the nice smooth ride that comes with everyone pushing, by insisting on being the only one pulling real hard from the front ? Who’s ‘out-of-step’ then, with only 1 pulling and everyone else pushing ? Seems like if you let it go that way with all that pushing and the slack ‘in’, it would be pretty hard to create a ‘slack out’ / ‘draft’ / pull/ tension situation that would break a knuckle or drawbar, right ? And can you ‘isolate’ - or wahatever you call it - the lead locomotive for a quieter ride - no, I mean, smoother train handling ? That way you too can sit up there and wave and chat nicely and have some tea with Ms. Roosevelt too, right ? [swg]
Seems like if you let it go that way with all that pushing and the slack ‘in’, it would be pretty hard to create a ‘slack out’ / ‘draft’ / pull/ tension situation that would break a knuckle or drawbar, right ?
At the risk of being condescending with a more detailed explanation -
Older grade crossing circuits are based on the track typically being divided into 3 insulated sections, called an ‘island circuit’ configuration. The middle section is usually real short, extending only for a few feet on each side of the crossing itself - but the outer or ‘approach sections’ that start the signal might be several thousand feet long, to provide adequate time for the signal to activate and come down, usually on the order of 20 to 30 seconds or so. The wheels and axles of a train bridging between the opposite rails complete a circuit that ‘shunts’ a relay in the crossing signal equipment cabinet and cause the signals to operate.*