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Saturday, February 9, 2013

PHOTOS: CPL Recycling at Landenburg Junction

Once upon a time in North America railroads were either seriously strapped for cash or railroad signaling hardware was abnormally expensive, but unlike today where re-signaling means installing 100% new signaling equipment and throwing out the old as recently as the 1990's it was common practice to reuse as much of the exigent hardware as possible. In today's post I will examine Landenburg Jct interlocking on CSX's Philadelphia Sub.

Today Landenburg Jct is hardly remarkable consisting of the end of a signaled siding on the mostly single track Philadelphia Subdivision. The Junction in Landenburg Jct refers to a connection with the Wilmington and Western Railroad, now a steam heritage line. I am not sure if this was ever a fully interlocked junction, but today the connection is not interlocked and the signaled siding interfaces with a small local freight yard. The CSX Philly sub used to be the Baltimore and Ohio railroads main line between Baltimore and Philadelphia and like many North American main lines it was operated as a two track line running single direction ABS. Because railroad interlockings used to be very expensive unless one was either the PRR or NYC they would tend to be used sparingly with simple crossovers and minor junctions being worked by hand with safety provided by timers and electric locks.

At some point, probably in the 1970's, the line was converted to a single bi-directional track with controlled sidings and CTC operation. However to save on costs much of the original ABS signaling hardware was retained. In the case of Landenburg Jct that means much of the original B&O Color Position Light equipment. At block signals the common practice was to simply move one signal over into the now empty trackbed to act as the reverse direction signal for the remaining track. I suspect that much of the track circuit logic from the old ABS line would have also been retained with some CTC modifications. An example of this type of block signal can be found a little to the south at Havre De Grace, MD.

The interlockings were a slightly different story as while a hand operated set of points could make due with protection by single direction ABS signals, and interlocking required signal protection on all routes. Extra signals could be installed, but back before the 1980's it was still common practice to install signals only to the right of the track they applied to due to the use of long hood diesel locomotives. Short of installing a new signal gantry, bracket or cantilever mast a dwarf could be installed governing the exit from the siding, but this could pose visibility problems and was susceptible to damage located between the running tracks.

However the B&O/Chessie System implemented a more innovative strategies to solve this problem that took the form of the bracket dwarf. This consisted of the original ABS signal for the removed/siding track altered to govern the new single main track with a dwarf signal attached to govern trains exiting from the siding. Here is what the bracket dwarf looks like at Landenburg Jct.

To allow trains on the main track to sight the signal that governs it over another train on the siding the mast must be extended to raise the CPL target up about 5-7 feet. Furthermore, because the dwarf is not visible a doll arm must be installed to indicate that a track intervenes between the signal mast and the track it applies to.

Looking at the rear of the CPL target we can see the old style termination box that indicates that this unit was recycled from the signals that predated the CTC installation. Also note the modern signaling cable snaking up to the box. Originally these wires would have been routed inside the mast itself.

A side view of the mast showing the wiring bundles to the new interlocking hardware.

The CPL dwarf for trains exiting the siding can display medium speed aspects over the #15 turnout at the interlocking. The B&O CPL system has its dwarf signals display the same aspects as its high signals.

Rear of the dwarf signal showing the GRS logo.

Here is a wider view of the mast showing the level crossing that is within interlocking limits. The level crossing equipment is not interlocked with the signals and routes can be lined without the level crossing protections being active. Also note the radio mast next to the interlocking relax hut. This is the ACTS data radio link that replaced the old pole-line to communicate commands from the dispatcher to the field station about 10 years ago. On the other side of the relay box is what appears to be the power supply from the local commercial grid and a field telephone box.

Here is a close-up of the relay hut showing the cables to the radio antenna and the PVC pipe based cable ducts to the field equipment.  This is a fairly modern relay hut indicating the interlocking was re-signaled recently, but before the time when it became policy to replace signals instead of performing cutovers. 

Now the signal leading off of the main track has a bit of an easier conversion. In this case all that was required was the addition of a 6 o'clock Medium Speed orbital and removal of any automatic signal number plates.

For some reason the central target of the main track CPL was replaced (or upgraded) when the interlocking was installed. One can tell by use of the smaller terminal box and general lack of rust.

Well that's all for now,.  If you are interested in other photos taken in this set you can find them here.


  1. According to Herbert Harwood's "Royal Blue Line" book, single-tracking occurred during 1958-1960, immediately after passenger service ended. It's a shame to see the magnificent two-track bridges (especially the Susquehanna River Bridge) being used at half of their capacity.

    1. Thanks for the info. When I originally wrote this I failed to recognize that the interlocking had in fact been re-signaled within the last decade with the older signals being retained.