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
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.
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 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.
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.
[?]Needless to say, I am confused.
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.
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:
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.
If the intermediate signals are one direction only on each track, it’s double-track.
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
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 an
Would UP’s on-going improvements to the Iowa transcon be correctly described as converting it from double-track to two main tracks?
I don’t have the employee timetable in front of me, but what I’ve seen in recent years of the new work is all 2MT.
Thanks very much for the replies and information folks. I appreciate it much,
To expand slightly - Back when ICG had two sets of tracks through central Illinois, it was apparently “double track.” I saw several instances where the station agent at Rantoul would hand up orders to a northbound which would then use the crossovers just north of the station to switch to the southbound track. When I asked the agent about it, he said that there was trackwork on the northbound track so they had to issue orders so the northbounds could use the southbound track.
I don’t recall that the track was signalled in both directions.
It probably was not - just in the direction of the current of traffic.
The SP had several Double Track situations, the busiest was between Sacramento and the Bay Area. Right had running. Signaled for right had running only. Should movements be necessary against the current of traffic, a whole gob of orders needed to be put out to everybody and entrance into that section of track that was being operated against the current was required to be flagged (Rule 99) an each entrance or corssover (if not at an interlocking or an open TO) and Rule 251 applied, or controlled switches and signals lined and locked for the move. Trains operating against the current of traffic almost always were restricted to Restricted Speed because they had no signal protection.
Interesting, I was not aware there was a difference in the two.
Yes. When ever a new portion of CTC is cut in, the general order revising the time table changes the Rule 6.3 column from DT - ATC to CTC 2MT - ATC.
Now if you read thru the special instructions for a particular subdivision, the Clinton Subdivn for example, there is a listing in part SI-04 MAIN TRACK DESIGNATIONS. It has Two Main Tracks: MP 2.1 to MP 202.2. That’s the entire subdivision including parts under DT and 2MT in the 6.3 column. Confused yet?
The Rule 6.3 column is for Main Track Authority. It tells what method of operation is used on the track(s), how a train or engine can be authorized to use the main track(s). The SI-04 tells you how many multiple main tracks there are and between what locations they are considered main tracks, but doesn’t give what authority is used. The reason you need to know is that there are rules that apply to operating on main tracks and some that apply to other than main tracks. You could have a stretch of multiple tracks that look to all intents to be main tracks, but technically are one single main and one auxiliary track.
Jeff
Freight trains operating against the current of traffic can run up to 49 MPH.
Here’s an example of a Rock Island (Uniform Code) Form D-R train order. It was issued on The RI’s east/west main line in eastern Iowa. Specifically that part of Subdivision 4 between Missouri Division Jct and West Liberty that was two main track Rules 450 - 453 territory.
TRAIN ORDER No. 210 Oct 26 1979
To C&E EXTRA 4515 WEST
At DURANT
EXTRA 4515 WEST HAS RI
A more important set of differences are capacity and cost.
Capacity: 2MT CTC is typically good for 70-75 trains per day average capacity, whereas double track is typically good for 45-50 trains per day average capacity. The difference lies principally in track maintenance restrictions. When engineering has track & time with 2MT CTC the railroad only loses to revenue service the section of main track between the nearest control points, which is typically 10 miles or less in U.S. practice, and trains running on the single track that remains in service can continue to run on signal indication at maximum authorized track speed, with following moves also proceeding on signal indication at maximum authorized track speed.
With double track the distance between control points is usually much longer – often as much as 100 miles – and while there might be hand-throw crossovers or center sidings with a spring switch at one end subdividing that distance into 10-20 mile segments, the crossovers and center sidings are typically hand-throw, if signaled typically nothing more favorable than a lunar, and thus restricted to 20 mph or less. One-half of the trains will be running against the current-of-traffic and cannot proceed on signal indication and require a verbal authority, and following moves against the current-of-traffic are greatly limited in frequency because they have n
Hopefully that’s not true now, is it? In the past Amtrak on the SP was allowed the usual 59 mph on such “unsignalled” track.