Datafever wrote: 1435mm wrote:What's confusing you?D.E. Husman's post is accurate. Maybe it is just me, but Ed's (first) post and Husman's post seem to be contradictory. I notice that you were thoughtful enough to clarify that it is Husman's post that is accurate. Thank you.
1435mm wrote:What's confusing you?D.E. Husman's post is accurate.
What's confusing you?
D.E. Husman's post is accurate.
Maybe it is just me, but Ed's (first) post and Husman's post seem to be contradictory. I notice that you were thoughtful enough to clarify that it is Husman's post that is accurate. Thank you.
I'm copying Ed's post because I can't think through too many things at once:
"You guessed right...double track means two tracks that see traffic in both directions,although some do have a "normal direction" of traffic movement depending on that railroads operating rules...two main tracks are often, but not always, run on a directional basis...main one for westward movement, main two for eastward movement.(or north and south, depends on the railroads preference and terminology)
Mainline tracks under CTC and ABS have their own set of paticular rules in the GCOR."
I think the first sentence is indeed unclear, in part. Double Track is a Method of Operation (a term of art) that is "current of traffic," either right-hand or left-hand, always, unless trains are running against current of traffic (which is an unusual condition). Two Main Tracks is a different Method of Operation where either track is regularly used in either direction. It is true, as Ed points out, that one track tends to be mostly eastward/northward and the other mostly westward/southward, but that is more due to the limitations of crossovers (too far apart and/or too slow) and train density patterns than because the railroad "has" to operate that way. On a well-engineered 2MT plant with a good dispatcher, you'll see lots of weaving of fast trains around slow using the crossovers. A poor dispatcher will run it as if it was double track and make no use of the plant's flexibility.
For what it's worth, most of us typically use "double track" in meetings and discussions to discuss construction of 2MT, because it rolls off the tongue faster, even though we all know it's technically and correctly 2MT. In formal documents we try to use the correct nomenclature, and in the employee timetable, it will assuredly appear the correct way!
S. Hadid
Murphy Siding wrote: Is it possible, that double track has crossovers, to allow for bi-directional running? Double track would be two, parallel tracks, where a train can't be switched from one track to the other?
Double track can indeed have crossovers but they are hand-throw and if a train uses the crossover it is now running against the current of traffic on the wrong track, and thus has no signal protection.
If you see crossovers in double-track that are signaled, they are not crossovers in double-track at all, but is CTC or an interlocking and it is multiple main track.
People do get confused by this stuff. It usually stems from people using definitions that are imprecise while the railroad industry uses definitions that are highly specific and limited, e.g., they see two parallel main tracks and think "aha, that must be double track." Well, it could be Double Track and it could be Two Main Tracks. To know which it is you need to either look at the employee timetable and see what it tells you; or, if you know something about signaling and Methods of Operation, you can study it and figure out which it is.
Rules of thumb:
1. Look at the intermediate signals (the ones with number plates). If the track is signaled in both directions with numberplated signals, it's two main tracks.
2. If the intermediate signals are one direction only on each track, it's double-track.
3. If there is two tracks that both appear to be mains, and neither is signaled, it could be dark double track. This is quite rare, however.
Double-track often begins and ends in control points that are, within their limits, short sections of multiple main tracks. Control points have to be signaled at all entrances, thus there will be a signal facing the "wrong way" on one of the double tracks. You can tell a controlled signal because it has no number plate.
Both mains and double track have crossovers, and specific rules as to how, when and who can use them.
One of the "rules" about main line crossovers requires the crossover to be restored or lined for the normal movement of traffic at all times, except when in use for the crossover, and requires the crew, if the switches are not controled by the dispatcher, to verbally confirm the switches are restored for normal traffic.
The same rule applies to sideings, you have to line back, and verbally inform the dispatcher or control operator that you have done so.
Shepard Texas, and the SC chlorine disaster are prime examples of what happens when this rule is not followed.
One of the additions to the rule now requires the locks on main lines switches to not lock unless the key is inserted, nor will they release the key untill the lock is closed.
You cant forget to lock the lock, unless your willing to forget your keys too.
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Double track implies that they are operated using a "current of traffic" method. The rule varies by rule book, but its sometimes referred to as rule 251 territory (or rule 9.14 if you use the modern GCOR). Trains operate in the same direction on one track and the other direction on the other track. It may only be signaled in one direction on each track.
Two main tracks are operated in either direction on either track. They are signalled in either direction on either track.
Typically double track is operated with ABS signalling and train orders (or track warrants) and two main tracks is operated with CTC signalling.
Dave H.
Dave H. Painted side goes up. My website : wnbranch.com
Thanks to Chris / CopCarSS for my avatar.
You guessed right...double track means two tracks that see traffic in both directions,although some do have a "normal direction" of traffic movement depending on that railroads operating rules...two main tracks are often, but not always, run on a directional basis...main one for westward movement, main two for eastward movement.(or north and south, depends on the railroads preference and terminology)
Mainline tracks under CTC and ABS have their own set of paticular rules in the GCOR.
In looking at employee timetables, for a given section of the railroad, I've found where the timetable will show sections as single track, sections as double track (DT) and other sections as two main tracks (2MT). What would the difference be between double track and 2 main tracks?
I'm guessing that one might be restricted to directional / current of traffic running vs. the other may be signalled in both directions, but that's just taking a guess.
Any help would be appreciated.Thx,
Stack
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