In the fall of 2014 CSX completed multi-year re-signaling efforts in the heart of its former Baltimore and Ohio territory that included the Philly, Capitol, Metropolitan and Cumberland Subdivisions. B&O style Color Position Lights, some installed as late as the 1990's, were replaced by the typical hooded traffic lights. Beyond the odd siding exit, drawbridge, diamond crossing or distant on non-signaled track, the main line CPL era east of the Ohio River was over. There was however one notable exception on CSX in the form of GREENBELT interlocking in Greenbelt, Maryland. Located just inside the Beltway adjacent to the DC Metrorail-MARC transfer station of the same name, GREENBELT was distinctive in being an interlocking that only really served the MARC commuter train service. These CPL signals would stand for an additional 6 years until their replacement in late 2020. In May of 2020 I went out to GREENBELT for a documentation run so I could present to you photos of The Last CPLs.
GREENBELT interlocking was installed in 1992 as part of a general
re-signaling of the Capitol Sub to better support the
MARC Camden Line.
This saw the elimination of any residual Rule 251 ABS territory, a new
Camden terminal complex in Baltimore and the closure of any remaining
manned towers such as JD TOWER in Hyattsville. Both the Capitol Sub project
and a similar one on the Metropolitan Sub turned out to be some of the
last where B&O CPLs were installed new. Like several of the new
Capitol Sub interlockings, GREENBELT was commissioned solely for the benefit of MARC
commuter trains and consisted of two side pocket tracks that would provide
an ADA compliant high level platform connection to DC Metro's new
Green Line terminus (The The Americans with Disabilities Act having
recently come into force). Pocket tracks were necessary as high level
platforms conflict with the clearance envelope of main line North
American freight trains. The interlocking consists of two switch pairs,
#1 and #2 and 4 signal pairs, 1E/1W. 2E/2W, 3E/3W and 4E/4W.
The signals were in turn broken down into 4 high mast CPLs for the main tracks and 4
dwarf CPLs for the pocket exits. The dwarf signals were placed
following the old "right hand" style, while the high masts were not.
In addition to the 12 o'clock orbital for normal routes, eastbound main
track signals sported 6 o'clock orbitals for Medium speed diverging
movements into the pocket tracks as well as 10 o'clock orbitals for
Approach Medium indications for crossover routes at AMMENDALE
interlocking,
one full signal block beyond GREENBELT.
Eastbound pocket track signals featured a 6 o'clock orbital for
diverging routes back onto the main line as well as an 8 o'clock orbital
for Medium Approach Medium indications when trains needed to
immediately diverge again at AMMENDALE.
The westbound signals have a slightly more complicated history. As originally configured westbound main track signals featured both 10 o'clock and 2 o'clock orbitals for Approach Medium and Approach Slow indications respectively. This is because GREENBELT was also one signal block away from the former
JD TOWER complex in Hyattsville. Trains approaching from the east would get an Approach Medium for track 1 to 2 crossovers or routes onto the Alexandria Extension at
RIVERDALE PARK interlocking. However if a Stop signal was displayed at
JD TOWER interlocking, a Slow Approach indication would be displayed (at least for diverging routes) at RIVERDALE PARK due to the short block distance between RIVERDALE PARK and JD TOWER. This then necessitated an Approach Slow capability at GREENBELT.
The westbound dwarf signals operated in a similar manner, just with a
full row of lower orbitals including an 8 o'clock orbital for Medium
Approach Medium and the somewhat rarer 4 o'clock orbital for Medium
Approach Slow.
