Double track vs. a lot of long sidings... when can you really call it double trak?

[JC UPTON]

Here in sourh Loiuisana, UP made some announcements a while back about installing double track between Livonia & St. James (crude treminal). 

We have seen a lot of work, but it seems that there will remain at least 2 bridges that will remain single track... 

**the 1st about 11 miles East (South?) of Livonia, a swing type draw bridge and associated west side approach about 3.4 miles long...

**the second at about 20 miles East (South?) of Livonia, a draw lift type (no longer operable) bridge and associated east side approach thru donwtown Plaquemine, about 0.8 miles long....

**additionally, there seems to be about 25.5 miles of rermaining single track segnments that have no apparent obstacles to DT, as yet no evidence of ungrade.

 

So the Question is:  what makes a true DT line?

[Wizlish]

Double track, in part, involves how the line is operated and signalled ... there are a number of places where 'two parallel tracks' are treated and dispatched as if they were two separate single-track lines.

I'm not sure the occasional 'bottleneck' restriction to one track necessarily disqualifies a line completely, since the restrictions are nominally short and 'unavoidable' physically for reasons of cost-effectiveness.  A hallmark, though, would be that both tracks be treated equally in approach (e.g., using a Y switch at each end of the restriction rather than a 'turnout' that gives priority to one or the other line geometrically).  I would also expect that dispatching would be conducted in such a way that track occupancy of a bottleneck by a train on one line would have minimal, if any, effect on the operation of trains on the other line, or that a rule like 'first come, first served' be applied to a required 'wait' at a bottleneck regardless of superior direction or other nominal considerations in train orders.

[jeffhergert]

When the time table says it's double track/two main track territory.

Jeff

[BaltACD]

jeffhergert

When the time table says it's double track/two main track territory.

Jeff

Says it all - no matter how long or short the segments are.

[timz]

Wizlish

A hallmark, though, would be that both tracks be treated equally in approach (e.g., using a Y switch at each end of the restriction rather than a 'turnout' that gives priority to one or the other line geometrically).

You don't think these trains have just left double track?

http://www.flickr.com/photos/barrigerlibrary/12353009664/sizes/h/

http://www.flickr.com/photos/barrigerlibrary/12352599705/sizes/k/

SP and most/all other RRs called double track double track, whatever kind of switch was at the end. No reason to say they were wrong.

Edit: in fact lots of RRs didn't use the term "double track". In any case the kind of switch at the end of it doesn't affect the name used.

[Paul_D_North_Jr]

In the 2 photo links posted by timz above, it's hard for me to tell that the 2nd main isn't a high-quality siding, except that it's at the same elevation and looks to be maintained about the same.  Especially the 2nd one - the spur to the right at the 'return' curve tends to make it look more like a siding than a 2nd main. 

To complicate this further, there's also an arrangement known as a "lap siding", where the 'inner' ends of 2 sidings - one on each side of a single-track main - overlap by a short distance (at least enough for clearance of 2 simultaneous train moves through it, up to maybe a couple hundred feet).  See about the middle of this webpage for a diagram of one:

 http://model-railroad-hobbyist.com/magazine/mrh-2011-06-Jun/mrh_qat 

Schematically it's the same as a short stretch of double track with a single cross-over in the middle; I believe the late and great model railroad track planner John Armstrong described it as just that.

As to wizlish's comment quoted just above: Envision a scenario where a single track was built first, such as across a bridge, in congested urban area, or worse yet, in a tunnel.  Then a 2nd track is to be added.  To install the Y-turnout as suggested would require realigning the soon-to-be double track portion of the existing 1st track that is to be paralleled, outwards by about half of the center-to-center track spacing to get it out far enough to then swing back into the Y-turnout, plus a slight curve at the far end.  That might be difficult to do on one side of the R-O-W, but easier on the other.  Hence, a more typical LH or RH turnout may be preferable.

- Paul North.   

[dehusman]

It doesn't matter whether its a left hand switch, a right hand switch, an equalateral switch, what the condition of the tracks are the size of rail or what they look like.  A track is a main track if the timetable shows it as a main track, double track or multiple main track.

If one looks at rule books, double track and 2 main tracks are not the same thing and may have different rules regarding their operation.

[blue streak 1]

Just to complicate matters more.  In the past the CSX A&WP sub in LaGrange, Ga had a signaled siding.  The siding was located where the old ACL lineville sub from Birmingham joined the A&WP at the south end of town and then Lineville sub diverged to Manchester at north end of town.

Several years ago CSX worked on the siding including closer tie spacing and reballasting.  A few weeks later CSX renamed the siding as Main track 2.  Later before starting the BNSF haulage trains Main 2 was extended on the Lineville sub toward Manchester and joined another siding there that became main 2.  Did not know if any work done before re naming.  Note:  All this track now is 2 MT on both A&WP and Lineville.    

[cv_acr]

Also note this important distinction:

 

A siding is NOT a main track, so speeds are limited to Slow/Restricted speeds under non-main track operating rules (105 in most rulebooks). Regardless of how nice the track might be.

If the second track is a main track, then higher speeds are allowable, subject to the maximum speed of the switches, track conditions and track speed limit, etc.

For example, the CN line near where I live is mostly single track with short sections of officially two main tracks rather than long "sidings". While the arrangement looks the same, the distinction is important. With Limited-speed switches at each end, trains can take the "siding" (actually a second main track) at 45MPH instead of 15.

[gardendance]

You big time railroaders sure talk big. How about us trolley guys for a while?

Ages ago, I'm not sure if it was before they changed from Red Arrow Lines to SEPTA, my dad took me on what I think was my 1st ride on the Media-Upper Darby trolley. I remember him mentioning that they had recently connected 2 sidings and he couldn't decide if it meant they now had 1 long siding or a short stretch of double track.

[K. P. Harrier]

To JC UPTON (8-6):

 

First, it looks as though you are relatively new here at the forum. Welcome aboard!

 

Second, the most important post line in your post is the last one, “What makes a true DT [double track] line?”

 

Third, as a west coaster, my personal familiarity with UP track in the Louisiana area has much to be desired.  Is the track in question associated with the east-west Sunset Route, or the north-south lines to Little Rock and Chicago?

 

Now, to address that important question:  “What makes a true DT line?”  Simply put, double-track is when two tracks are generally each operated or signaled in only one direction from Point A to Point B.  The emphasis therewith is on the word ‘line.’  It may have a short single-track bridge to traverse, but overall it is considered a double-track LINE.

 

Technically speaking, though, when one gets away from the broad word ‘line’ (A to B), the commonly understood railroading terminology of ‘double-track” and “two-tracks” comes into play, and only refers to a specific segment on a line, anywhere from Points K to L, etc., or all the way from Point A to Z.  If a track (of two) is only operated or signaled in ONE direction, then it is Double-Track.  If the section is operated or signaled in both directions, it is Two-Tracks.

 

My suspicion is the line (A to B) you made reference to is a single-track one, but is having short sections of two-tracks installed or planned.  In that case, your inquiry is an illogical one that technically doesn’t make sense; but don’t feel bad, JC UPTON, the best of us here at the forum put a foot in the mouth from time to time.  I do more than I would like to admit …

 

Anyway, it is hoped your inquiry has been satisfactorily addressed (and NO rocks come flying my way from the forum).

 

Enjoy the forum and take care,

 

K.P.

[blue streak 1]

cv_acr

For example, the CN line near where I live is mostly single track with short sections of officially two main tracks rather than long "sidings". While the arrangement looks the same, the distinction is important. With Limited-speed switches at each end, trains can take the "siding" (actually a second main track) at 45MPH instead of 15.

 

That may be true for CN.  BUT:  Here in local CSX territory at one time all sidings would display a red over yellow signal for trains diverging into a siding.  Late 1990s CSX started making unsignaled sidings display red over luna for entering unsignaled sidings calling for restricted speeds in the sidings and still does if siding occupied.  If Red over yellow siding speed ( not more than 30 ) prepared to stop at next signal.  If signal displays a red over yellow and a third head  yellow, green, red, luna expect same at next signal.

So know of two sidings that have displayed red over yellow, then red over luna, and back to red over yellow over time.  Third head displays can be any of above or more.

NS is still using red over yellow into some restricted sidings.  Confusion by an Amtrak engineer entering one of these NS sidings resulted in a rear end collision into a stopped freight. The engineer was used to other locations using the red over luna.

Any one know if the CSX new super sidings are listed as sidings or 2 MT ?

[timz]

cv_acr

A siding is NOT a main track, so speeds are limited to Slow/Restricted speeds under non-main track operating rules (105 in most rulebooks).

No idea if that's true in Canada-- it's not true in the US.

The Metrolink 2002 timetable shows 79 mph on two "Controlled Sidings" on the single-track SFe 2nd District betw San Bernardino and Claremont. One is 11000 ft and one is 8100 ft, and it's 45 mph over each siding switch, so you wonder why they bothered.

[timz]

Paul_D_North_Jr

In the 2 photo links posted by timz above, it's hard for me to tell that the 2nd main isn't a high-quality siding

Just looking at the pic, that's true. If you know where the pic is then you know it was the end of double track at the time.

https://www.flickr.com/photos/barrigerlibrary/12330677614/ (backwards)

https://www.flickr.com/photos/barrigerlibrary/12330553854/in/album-72157640346919596/

https://www.flickr.com/photos/barrigerlibrary/12529018634/in/album-72157640346919596/

https://www.flickr.com/photos/barrigerlibrary/12684356744/in/album-72157640346919596/ (backwards)

[Paul_D_North_Jr]

In right-hand running territory, the preferred turnout leading from the single track into the double track/ 2 main track portion would be - all else being equal - a left-hand turnout, not a wye or a right-hand turnout. 

Why ?  Minimizing switch point (and frog and guard rail) wear.  With a left-hand turnout, the 'facing point' move from the single track onto the 'going away' track is the right straight route, hence minimal wear on the left switch point.  The move from the left 'coming towards' track to the single track is the curved route, but since it's a 'trailing point' move, the wear on the curved (right) switch point is minimized.

With a right-hand turnout, it's just the opposite - all of the 'going away' moves use the right-hand curve and hit the curved (left) switch point as a 'facing point' move, which usually causes maximum switch point wear.  All of the 'coming towards' moves trail through the straight side of the switch, so minimal wear on the right switch point, which is essentially the same as for the left-hand turnout.

The wye-type turnout is a hybrid of the above; but as such, it has 2 'facing point' moves - 1 on each side, which would cause some wear on each switch point.  However, that's not quite as bad, since the degree of curvature is usually much less than for a 'straight-sided' turnout.  

All of the above is just as valid for the frog and guardrail, and for about the same reasons, but would take too long to explain in detail.   

- Paul North.   

[Deggesty]

Another word (for any newbies) concerning operation on two tracks that are each signaled for movement in one direction--if the DS lets you move on the wrong main, you are moving in dark territory for you have no signals indicating the track condition ahead. If you line a crossover to move to the wrong main I understand that you have to wait five minutes before making the move--just in case there is oncoming traffic on that main.

I just realized that in the only instance of backing onto the wrong main that I know of, the freight did not wait, but began using the crossover just as soon as the caboose reached the first switch for the engineer continued backing until he had passed the fouling point of the northbound switch--and the City of New Orleans was right at the fouling point of the southbound switch (I was on the east side of the track so I could not tell if it had stopped at all; I do not doubt that it had stopped at the next signal north of the crossover).

 

[JC UPTON]

K. P. Harrier

 

Third, as a west coaster, my personal familiarity with UP track in the Louisiana area has much to be desired.  Is the track in question associated with the east-west Sunset Route, or the north-south lines to Little Rock and Chicago?

 

 

K.P.:  Thanks for your welcome...

**  My father retired from the S.P. out of New Orleans...he was a fireman, later engineer, and operated on the eastern end of the "Sunset Route" ("Morgan's Route", between Avondale and Lafayette via Morgan City, now part of BNSF), as well as local interchange duties, and other types of locals...

 

**  To your question, the "line" involved is part of the old Texas Pacific / MP Terminal, between Livonia LA & Avondale LA.  It is (probably) a single track, now being upgraded with new  or longer sidings.  It would have been part of an east/west route into New Orleans, north of & parallel to the old Sunset Route.  It is now the main line into the New Orleans area.   Livonia is a junction & classification yard, about 40 miles west of Baton Rouge, where the (now) UP main from Beaumont joins a line from Shreveport.

My question came from your posts about “two tracking” at TEHACHAPI and (your end of) the Sunset Route compared to what I am seeing happen here.  A related factor was the local newspaper reports when UP announced the upgrades here in early 2014…

 

https://www.uprr.com/newsinfo/releases/capital_investment/2012/0613_louisiana.shtml