Signals 46/48, Hansrote, WV, Cumberland Subdivision, 5/13/2001
	Interlocking signals, McMillian, WV, Mountain Subdivision, 5/8/2001
	Block signals, Amblersburg, WV, Mountain Subdivision, 5/8/2001
	Dwarf signal, Keyser, WV, Mountain Subdivision, 5/10/2001

   B&O's CPL signals have been a distinctive feature of all lines radiating from Cumberland, MD, and indeed most B&O main lines everywhere.

   The first permanent installation for B&O CPL's was on the Staten Island Rapid Transit, when it was electrified beginning in the summer of 1924. This gave the B&O an opportunity to operate the new signal system in a heavy traffic situation. SIRT had the highest density passenger train traffic of any B&O or B&O subsidiary divison.

   The second installment was along the 12 mile Perth Amboy Subdivision between Clifton Jct and Tottenville as electrification progressed. The Tottenville line began full electric service July 1, 1925. The SIRT North Shore line from St. George to Arlington was electrified by late 1925. After these prototype installations, the CPLs became the system standard.

   Even though CSX is replacing these signals with the modern "traffic light" style installations, there are still numerous CPLs left on the B&O parts of the system. The Keystone and Cumberland Terminal Subdivisions' conversions are complete as of 12/2002, but both the Mountain and Cumberland Subs still have them in many places, including a few on bridges and cantilevers.

Signal Aspects & Indications According to the 1941 B&O Rules and Regulations of the Operating Department.
(Clear - Rule 281) Proceed.	(Medium Clear - Rule 283) Proceed at medium speed within interlocking limits, or through non-interlocked switches immediately beyond the signal. Block clear.	(Slow Clear - Rule 287) Proceed at slow speed, approaching next signal at slow speed.
(Approach Medium - Rule 282) Proceed, approaching next signal at medium speed.	(Medium Approach Slow - Rule 283B) Proceed at medium speed, approaching next signal at slow speed.	(Approach Slow - Rule 284) Proceed, approaching next signal at slow speed. Train exceeding medium speed must at once reduce to that speed.
(Approach - Rule 285) Proceed, preparing to stop at next signal, and be governed by indication displayed by that signal. Train exceeding medium speed must at once reduce to that speed.	(Medium Approach - Rule 286) Proceed at medium speed, preparing to stop at next signal and be governed by the indication displayed by that signal.	(Slow Approach - Rule 288) Proceed at slow speed, preparing to stop at next signal and be governed by indication displayed by that signal.
(Stop - Rule 292) Stop.	(Permissive Stop - Rule 291) Stop, then proceed at restricted speed until entire train passes next signal.	(Medium Approach Medium - Rule 283A)Proceed at medium speed approaching next signal at medium speed.

   Memorizing signal aspects and their meanings can be hard at times. As for the B&O CPLs, there's a fairly easy way to do it.

• On the Main Head: green means "Proceed", yellow means "Prepare to Stop", red means "Stop".

   The lunars/yellows have two indications:position vertically and position horizontally.

• Vertically: Above the main head it's track speed from here, below it's medium and none is slow.
• Horizontally: Next signal is track speed if in the middle, medium if on the left and slow on the right.

   This series of pictures taken at Hansrote on the Cumberland Sub illustrates a train passing a CPL. The proceed indication goes off, and after a short delay the permissive stop indication comes on. Depending on the circuitry, a restrictive indication might be displayed while the relays complete their cycles.

Q134 eastbound passing the Hansrote CPL on the Cumberland Subdivision, 5/13/2001. (click for a larger image)

   Suggested links for further reading on the topic of CPLs and signalling in general:

• Carsten Lundsten's US Signalling website.
• Mark D. Bej's Railway Signalling and Operations FAQ.
• James P.G. Sterbenz' Rail Signal Page.

   Thanks to Carsten S. Lundsten and Ed Bommer for their help in preparing this page.