The inevitable impossible - PTC is down!!!

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Re: The inevitable impossible - PTC is down!!!

Postby Tadman » Mon Aug 14, 2017 7:46 pm

twropr wrote:Today Amtrak.com shows #353 leaving Kalamazoo at 2:31 pm and arriving Niles at 3:03 pm. That's a 48.6 mile run, averaging 91.1 MPH, so I'd have to say that ITCS is back on this segment.
Andy


I think the same, I was on 353 today and it was on time and felt a bit fast for 79. The trains have been consistently 20-30 minutes late when ITCS was offline this summer. Of course, that didn't stop us from being 30 down into Chicago but that was due to NS track work.

And now I'm on a brand new 737 headed for Dallas with a bourbon. Wish I had the time for the Eagle but this week is batsh** nuts and no time. Maybe on the way home.
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Re: The inevitable impossible - PTC is down!!!

Postby David Benton » Tue Aug 15, 2017 8:00 pm

they have 2 rails everywhere the train goes obviously, why can't they just send data over them ? Like wifi over power lines. I know they are not insulated , but I would think todays technology could still get a signal through them.
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Re: The inevitable impossible - PTC is down!!!

Postby mtuandrew » Tue Aug 15, 2017 8:30 pm

For a fair distance, sure, you can get signals through a rail. That's how (EDIT:) CTC and ATC pulse-code cab signal systems and all grade crossing signals work. The problem is tracking the train's location, velocity, and potential obstacles and transmitting that data between signal and locomotive. Rail doesn't broadcast like that.
Last edited by mtuandrew on Wed Aug 16, 2017 1:15 pm, edited 1 time in total.
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Re: The inevitable impossible - PTC is down!!!

Postby David Benton » Tue Aug 15, 2017 8:59 pm

not so sure it is not possible. But I would have thought you would still have transponders to actually communicate /locate with the train. just they would send their data through the rail .
They can do some pretty amazing things with electronics now. They can locate faults/ shorts in cables 100 of metres long , just by sending a pulse through them.
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Re: The inevitable impossible - PTC is down!!!

Postby Nasadowsk » Tue Aug 15, 2017 9:27 pm

So, would LZB be or not be compliant? It pretty much does the job and has been around since the AEM-7s started running....
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Re: The inevitable impossible - PTC is down!!!

Postby mtuandrew » Wed Aug 16, 2017 1:13 pm

Nasadowsk wrote:So, would LZB be or not be compliant? It pretty much does the job and has been around since the AEM-7s started running....

I mean, it sounds like an analogue to pulse-code cab signalling with Automatic Train Control, so kind of a PTC system without as precise of train locality monitoring or trackside collision protection. The European Train Control System seems like the closest analogue to ACSES (but more advanced, obviously.)
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Re: The inevitable impossible - PTC is down!!!

Postby SRich » Wed Aug 16, 2017 4:26 pm

Nasadowsk wrote:So, would LZB be or not be compliant? It pretty much does the job and has been around since the AEM-7s started running....

If you talking about the German version, yes indeed LZB(continues signal control) its has over it's full track lengte cables installed. The cables provide the train computer with signal information, speed and location. The train can talk back to the "tracks mounted cables and correct its location with the appropriate info.

It's work really good, but its very expensive, so the only use today is the German high speed rail lines, and it would be replaced with the most crappiest system of the planet ERTMS level 2 and 3....
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Re: The inevitable impossible - PTC is down!!!

Postby justalurker66 » Wed Aug 16, 2017 8:55 pm

David Benton wrote:not so sure it is not possible. But I would have thought you would still have transponders to actually communicate /locate with the train. just they would send their data through the rail .
They can do some pretty amazing things with electronics now. They can locate faults/ shorts in cables 100 of metres long , just by sending a pulse through them.

I think the other way around. The track is an excellent way of locating the train. Sending codes from wayide through the rails that are shorted by the trains wheels. The wayside equipment can calculate the train's distance and speed (and even provide constant warning times for crossing protections so the fast Amtraks and slow freights trigger crossings with the same timed amount of warning instead of having gates come down way too early for freight trains).

Wayside radio systems can transmit more detail that cannot be transmitted through the rail. Alarms from crossing gate malfunctions, track restrictions, warrants, other messages. While cab signalling is currently transmitted via the rails it is a simple message. Not as complex as the data that can be sent via wayside radios.

Some systems rely on GPS. And while GPS can (with difficulty) be faked even when it is working one would need precise accuracy to tell the system which track of a multi-track railroad the train is on. Most likely a ground based correction system. I'd prefer to rely on track based detection systems, where available. But having a GPS input to assist in locating trains would be helpful.
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Re: The inevitable impossible - PTC is down!!!

Postby mtuandrew » Thu Aug 17, 2017 8:38 am

Beyond safety, the main goals of PTC are to increase capacity and speed through rolling block protection, rather than fixed automatic block signals. I-ETMS and ACSES need to prove their worth safety-wise first though.
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Re: The inevitable impossible - PTC is down!!!

Postby justalurker66 » Thu Aug 17, 2017 10:57 am

Some systems will have additional features "beyond safety". Mandated PTC does not require the add ons that some railroads will implement.
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Re: The inevitable impossible - PTC is down!!!

Postby electricron » Sat Aug 19, 2017 1:14 am

While they can use the tracks for local signals and controls, you can't use the tracks to send electric signals over long distances. It doesn't matter how large a conductor is, electricity takes around a 1,000 volts per mile to push that signal. The size of the conductor, in this case the track itself, allows more current flow. To have a train dispatcher be hi ndreds, if not up to a thousand miles away, you're going to need transformers along the way to step up the voltage of the signals. Since tracks are located at grade exposed to humans and other animal life, the voltages can't be too high on the tracks.

Shunting zones are usually isolated sections of tracks on opposite tracks, a train's wheels and axles providing the shunting path for the local signals, like a light switch at you home between two contacts. These sections of tracks for the shunts are isolated by insulators from the rest of the tracks. That's why crossing signals aren't actuated miles away from the crossing.

Additionally, mixing power and control signals on the same conductor (in this case tracks) isn't a great idea because noise and interference over long distances. There's a reason cat 5 wires for your Ethernet cables are shielded, even for distances as short as 6 feet.. Steel tracks rust away, and in different environments electrical catholic protection is needed. So there are already some low voltage, low current power electric currents in the ground near tracks anyways.

There's a reason why telephone companies are switching from microwave towers to glass fibers for communications recently. It's actually cheaper and easier to do so. In the not too distant past, railroads ran the signaling on many separated circuits and wires on telegraph (telephone) wires on poles above the ground, do you really believe they could have used the tracks themselves instead of using copper wires hung from wooden poles? They didn't, and you can't do so today. Other means of communications have replaced those wires on poles spaced 200-300 feet apart, but they haven't been using the tracks!
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