Caught on Camera: Clear to Next Interlocking

Also known as NOARC Rule 280a, this special cab signal related signal was invented by the Pennsylvania Railroad for their experimental trial of cab signals without fixed automatic signals (today known as Rule 562) on the Conemaugh Line between CP-CONPIT and CP-KISKI back in the late 1940's or early 1950's.  Without wayside intermediate signals, trains that experience a cab signal failure en route would not be able to proceed without absolute block protection ahead.  Normally this would involve train orders (or today a track warrant/Form D) however the reliability focused PRR decided to automate the potentially delay inducing procedure with a special signal that would illuminate when the track was clear to the next interlocking where the next wayside signal would be located.

 One option could have been to simply display a Rule 280 "Clear Block" signal, which was an upper head | with a single marker below and used in manual block territory.  However because of the lack of manual block distant signals and because of the non-lack of train detection, a new Rule 280a was created, "Clear to Next Interlocking" and it would consist of a flashing lunar white market offset to the side and labeled with a reflective 'C'.  Any diverging movements through the first interlocking would be covered by the fixed signal and trains would be instructed to approach the next interlocking prepared to stop.  Here we can see an example of a Rule 280a being displayed along side an Approach signal at Amtrak's REA interlocking.



As you can see, the 'C' lamp is displayed independently if absolute block conditions are met.  On unit lever and VDU interfaces the 'C' lamp is a separate switch associated with each signal.  While technically unnecessary at back-to-back interlockings, 'C' boards are more often deployed uniformly so crews do not loose track of which signals they can pass with failed cab signals. In this more elaborate demonstration of signal progressions at Amtrak's HUDSON interlocking we can see how the 'C' lamp is placed on the fame flashing circuit as other flashing signals such as Cab Speed and Approach Limited.



Finally, we actually have an example of a display 'C' signal in the wild.  This was at the re-signaled STELL interlocking for a southbound movement against the flow of traffic on the NS Enola Branch.  NS has decided to employ waysideless operation on much of it's cab signaled PRR territory, following in the footsteps of Conrail in the 1990's.  Previously the Enola Branch had been run under single direction Rule 251, but when the line was re-signaled, the Rule 562 operation saved a bit of money on intermediate signals.  First note the NS style backings on the 'C' boards, a practice not carried forward to subsequent projects. Second this is an interesting occurrence as a train with failed cabs could in theory be swapped out at Enola yard and finally note the slower flashing cadence compared with the Amtrak signals.



That's it for this episode of Caught on Camera. Nothing is scheduled for the next time cause I won't know it until I catch it ;-)