Reversable signal system.

[rs3bob]

In an article about the New York Central, in a November 1950 Railroad magazine, there is mention of the reversible signal system on the multiple track fanning into the Grand Central Terminal. What are reversible signals? The question is do they physically turn and face the other way? Any help in understanding this type of signal would be helpful.

[daveklepper]

On the four tracks between Mott Haven Junction and Grand Central Terminal, there are two sets of signals, one for each direction, on each of the four tracks.   In the cut, on the embankment, and one the elevated structure, they are located on signal bridges because of the close track spacing.  In the tunnels (in general, three tunnels, one double-track in the center, and one single-track on each side) they are conventional vertical signals bracketed off tunnel walls except for those between the two center tracks, which are on stands.   They are all color-light signals, mostly two displays, some three displays leading to switches ("turnouts") or advance signals for such signals.   In the throat trackage on both levels there are dwarf signals with only one indication, and in many cases this is either yellow or red, with no green.   When last seen, the dwarf signals used movable color screens behind a fixed lens, but something more modern may be use today.

Also, Metro North is in the process of generally replacing all wayside signals with cab signals and automatic speed and train control protection, not replacing the engineer, but taking control if the engineer exceeds restrictions.  I am uncertain whether this replacement has progressed to this most vital four-track section, which was intended to be the last step in the electrified zone.   In the areas where the replacement has occured, the only wayside signals are lunar white before switches (turnouts) which simply indicate that everything is working properly and the cab signals can be assumed to show correctly conditions ahead and the locked position of the switch or switches.

I believe all switches are now controlled from a dispatcher's CTC panel at GCT.   But around 106th Street, on the embankment, there was a tower, unique in that in only controlled switches between the four tracks with no diverging route away from the embankment.  This tower bridged the four tracks like a huge signal bridge.   I wonder if it still there.

The south end of either of the two 125th Station platforms is a great place to photograph passenger trains.   A great variety of equipment and a wonderful skyscraper background.

[clarkfork]

Reversible signaling means that there are signals on each track facing both directions, to GCT and away from GCT, or north and south  The signals did not actually move.  They were/are mounted back to back, one signal facing 180 degrees from the other.

In that era most multiple main track was signaled for only one direction, usually the right hand track on double track.  On multiple main tracks each track was assigned a "current of traffic."  And is was common that the track had signals facing only for that direction.  There is still some of this sort of signaling around. BNSF between Minneapolis and Fargo has several stretches of double track signaled for only one direction, the normal current of traffic.  UP has the same west of Omaha to Gibbon, NE, and there are some others.

Back in 1950 multiple track signaled in only one direction was the norm.  GCT's four tracks which had signals facing both directions was exceptional.  Today, almost 60 years later, most multiple main tracks are CTC controlled and have signals facing both directions.  But this was unusual in 1950.

[wjstix]

I assume the reason for this set-up was commuter trains, making it easier to use all available tracks for trains to arrive or depart without having to change tracks during rush hours??

[henry6]

It, in some ways, was a percurser to CTC.  Designate tracks were signaled in both directions between given interlocking stations. Reversing the traffic on a given track was done either by timetable authority or by permission of the dispatcher. Then the two (or more)  interlocking operators would make the change with the operator originating the train movement making the request electically so as to change the signal indications and interlock the route. Yes, this was more common in high density commuter territoreis.  The DL&W had the middle track from Millburn, NJ to Newark, NJ on its three track main that was reversable (still is) and both tracks 1&2 between Denville, NJ and Dover, NJ. The CNJ, as I remember, had four tracks, at least through Bound Brook, NJ with reversable signalling back in the 1950's.  CTC of course, and today's computerized systems, eliminated the on site interlocking towers, so reversing traffic is mostly in the hands of the dispatchers. 

[daveklepper]

The New York Central's reversable signalling between Mott Haven Junction and Grand Central Terminal dates from as far back at WWI!   The selection of signals for one or the other direction was controlled by the towers, one at the throat at GCT (there were two other towers at GCT controling the upper and lower level platform and storage tracks and the approach tracks), the tower at 106th Street that was a bridge spanning the four tracks, and the tower at Mott Haven.   There are also, still today, a full set of crossovers around 106th Street.  In addtion to insuring good continuity of service when one track was under maintenance, the arrangement gave needed flexibility in providing the service.   On occasions I saw the four tracks run as two separate double-track lines, with the eastern pair of tracks devoted to Harlem and New Haven trains, and the western pair, less used, only to Hudson line trains.  This eliminated crossover moves at Mott Haven.  I have also seen the two outer tracks used in the direction of the rush hour, south in the morning and north in the evening, plus one of the two inner tracks, with only one inner track used in the direction opposite that of heavy traffic.   I have seen these operational arrangements used under all managements, New York Central, Penn Central, Conrail, and Metro North.  As a youngster, 1936-1949, frequently rode the head-end of mu's on line, years 1949-1954, frequently rode NYNH&H New York - Boston, ditto 1957-1970, and 1971-1996 was a regular Harlem Line reverse commuter, often riding the head end.