General Discussion

al-in-chgo:

I had no idea there were so many new bridge-style signals.  Back here in the Midwest/East, I am more struck at how the old bridge signals are being torn down (or allowed to stand, but inactive) in favor of simpler lights, often the three-position type. 

What you are seeing being torn down are signal bridges and cantilevers that date to the ICC regulation that wayside signals had to be to the right-hand side of the track governed.  That rule disappeared, oh, around 1970, with the proviso that if a left-hand signal was used, it could not possibly be confused for a right-hand signal governing an adjacent track.

In new construction, however, the rule on most railways is that signal masts cannot be placed between tracks with centers less than 20 feet, in order to obtain adequate clearances for men and equipment.  But in some locations, it is not economically feasible to obtain 20-foot track centers and put a signal where it cannot be confused as to which track it governs, so in those locations a signal bridge or cantilever is used instead of the mast signal. 

For example, suppose a railway is two-main tracks (movement in either direction on either track) with 15-foot track centers.  If the wayside signals date to pre-1970, the left-hand track in either direction of movement will require either a signal bridge or cantilever to place its signal to its right-hand side (between the tracks).  (However, if it is "Rule 251" current-of-traffic territory, there is no reverse-signaling except at end points, so no need for reverse signaling and no requirement for signal cantilevers or bridges, if it is right-hand running.  But if it's left hand running, then every signal will be on a bridge or cantilever.)

Now suppose that railway is resignaled with modern equipment today.  The bridges and cantilevers are no longer needed and new masts can be erected "field side" or left-hand to the direction of movement instead of right-hand.

Now suppose we're building a new two-main track railway today, with 20 foot track centers.  All the signals can be mast type so long as all we have is two main tracks. The intermediate signals will in most cases still be placed field side on both tracks because it saves a mast, is safer, and is cheaper, and there's no chance for confusion so long as all are paired. 

But at some locations, where there is a track at a 15 foot center, the bridge or cantilever will still be needed.  Suppose there is an outside siding or runner parallel to one of the two east-west main tracks.  For sake of illustration, let's say it's on the south side of the two main tracks (north main is #1, south main is #2).  That siding is on a 15 foot center from its nearest main track (because in most cases, it was built a long time ago.)  At the west end of the siding a mast-type signal can be placed on the field-side of the siding to govern movements leaving the siding and entering main #2.  A mast signal can be placed between the main tracks to govern westward movements on the #2 main track, and a mast signal can be placed to the outside (north side) of the #1 main track to govern westward movements on the #1 main.  Every signal is to the right side of the track it governs and there's no opportunity for confusion, because a signal for another track is always on the far side of the other track.

At the other end of the siding, however, we need a cantilever for the eastward signal on the #2 main, because there is either not room for the mast signal between the siding and the #2 main track to govern eastward movement on the #2 main, or we risk creating a confusing signal placement by putting the eastward signal for the #2 main to the left hand side of the #2 main, and the eastward for the #1 main to the left of the #1, which makes the east CP signal placement the opposite to the west CP signal placement at the other end of the siding.  That is how you set up an engineer for an error and cause collisions.  I know of a fairly recent head-on with multiple fatalities that several of us think was caused by confusing signal placement and an engineer unfamiliar with the territory:  he read the signal governing his main track as applying to the other main track.

If we're just dead set on getting rid of all new cantilevers and bridges, the solution is to spread track centers to 20 feet.  That can get rather expensive if we're in the vicinity of overpasses that don't have sufficient width between their piers and abutments because we'll have to build a new overpass (think of an 8-line highway bridge with adjacent interchanges, utility crossings, etc.), or in the vicinity of bridges over waterways that weren't built for 20 foot centers, which can also be multi-billion dollar fixes.  It can mean having the toe of fill move off the right-of-way, which in a best case is a land acquisition from a reasonable landowner at a reasonable price, and in the worst case moves large buildings, or triggers a programmatic Environmental Impact Statement , or triggers 404 wetland permits, or comes up against a hell-no-see-you-in-the-Supreme-Court landowner, and we'll maybe finally get to build the railway long after we're all dead.

So, long story short, that is why it is often feasible to tear down old cantilevers and bridges en masse, but in some cases -- particularly complex interlockings and CPs -- why there is good reason to build new signal bridges and cantilevers today.

Update as of Tuesday, May 26, 2009

West Colton Yard, East of Pepper Ave.

This date found hardly anybody tending the fort, so to speak, and very little progress had been made since the last update. 

The exception was the easternmost (farthest back) turnout, which now appears complete

Last week the same turnout needed much work, as seen below

The following story appeared in this week's edition of the Maricopa (AZ) Monitor:

The proposal will have second rail lines placed across four Maricopa intersections, including Arizona 347. '); } //--> Union Pacific spokesman Luis Heredia said earlier this month that plans with the city have already been made to do a shoefly-style bypass around the Arizona 347/UP crossing while the work is being done. The work, he said, should take no longer than one weekend to compete, though no timeframe has yet been given for when that will occur. '347 is an outlier that we want to complete as soon as possible,' Heredia said. Union Pacific's double-tracking project as a whole has been slowed due to the economy, with plans to finish the 757-mile stretch spanning from El Paso to the southern coast of California being pushed back from 2010 to 2012. The Maricopa intersections, and Arizona 347 in particular, should be completed in the coming weeks.

©Casa Grande Valley Newspapers Inc. 2009" I don't quite understand the need for a shoo-fly if the crossing work on STH 347 is only going to take a weekend.  It seems that in the past they have closed the railroad down at least that long for construction.  As to the "2012" completion date for the entire project El Paso to LA, I hope they can meet that timetable. John Timm

The primary concern is emergency vehicle travel times via alternate crossings, locations of fire and EMS stations, and traffic congestion on alternate routes.  It's worked out in detail months in advance for each crossing, and if multiple crossings are affected simultaneously a detour and emergency vehicle plan is worked out for the total picture, and public agencies participate in the discussion.

RWM

 John and K.P., thank you each for your updates!

 K.P., please keep us updated with whatever they seem to be doing at West Colton.  Looks interesting.

desertdog:

[img[\img] Looking east from the Maricopa Amtrak platform to where there was a team track until a few months ago. There is newly spread gravel on both sides of the tracks, but the second main will be on the right hand side of the current main. In the far distance on the left you can make out the hooded signals at what will be East Maricopa, most likely the place where eastbound Amtrak will make a diverging move to the right. The welded rail will be used for replacement on the current main. John Timm

I could have been a little more complete in my description here.  This is one of those transition areas where the existing main will shift from being on the north side of the ROW to the south side of the ROW, which explains the gravel sub base on both sides.

John Timm 

Desertdog (5-30):

Seeing you posting photos of Maricopa was great!

Interestingly, I was just in Maricopa a few days ago, and know exactly what you were relating in your post.

UP seems to be putting in TWO overlapping signal systems there!  Because of that, I perceive some fascinating things about the future.

An upcoming multi-post, multi-day report from Arizona to New Mexico has been prepared for the forum, and will follow the following schedule:

Part I:  East of Shawmut, AZ to CP887 – Tuesday, June 2

Part II:  East of CP SP887 to West of MARICOPA – Thursday, June 4

Part III:  Solving the Mysteries of Maricopa – Saturday, June 6

Part IV:  East of Maricopa to Tucson – Monday, June 8

Part V:  The Cienega Creek Track Identification Issue – Wednesday, June 10

Part VI:  Eastward into New Mexico – Friday, June 12

A teaser …

The above photo taken in Maricopa relates to THREE signal systems … and will be dealt with in Part III

K.P.

PS:  In posting photos herein, desertdog, if they are not exactly 640 x 480 in size, they wreck havoc with past and future posts on the page!  It is a quirk in the Kalmbach forums.  I’ve had to resize some photos to straighten out some posts I’ve unwittingly messed up.  But, even that didn’t correct everything!  Like I said, quirk is the word!

Update:  Arizona-New Mexico

Part I of VI:  East of SHAWMUT, AZ to CP SP887

We start east of SHAWMUT and encounter this new intermediate mast amid cactus, hilly terrain, and single-track

The west signals of the new [CP] ESTRELLA.  Because of visibility problems for those unable to access railroad property, it is indeterminate exactly how far westward (rightward) the new second-track is laid, IF it even is laid, but this is the beginning of two-track operations eastward (leftward)

An unusual device at [CP] ESTRELLA:  They are springing up all over the place.  California is not immune either.

CP SP882 MOBILE is NOT a crossover, but the west end of the MOBILE siding.  The west end of MOBILE also has one of those blue light devices (far right).  Note the bi-directional heads on the left mast (for Main 2)

The west end of that siding has a cantilever structure governing westbound movements for Main 1 and the siding

The east end of MOBILE uses just poled signals.  From left to right, the first and third masts are directly across from each other on the east portion of the CP, while the second and four signals govern the siding and Main 1

From 83rd Ave. (M.P. 886.32), looking west:  Highway 238 is on far right

The 83rd Ave grade crossing is a marvel with barbed wire fencing, cattle guard in the roadway, and just a well manicured visual site

Interesting signage too

Looking east from 83rd Ave toward the new CP SP887 double-crossover

Part II is scheduled for Thursday, June 4; and runs from east of CP SP887 to west of MARICOPA

Once again KP thanks for the latest updates on the Sunset route. Are you and I the only two California residents up this early and on the forums. Must be insomnia. Actually I like getting up this early and working on tax returns for clients that are on extension. And this year I have never seen as many tax clients on extension.

Al - in - Stockton.