If one scours enough interlocking diagrams it is easy to find examples where what might meet the signaling definition of a "straight" or Normal Speed route provides a more restrictive signal indication in order to deal with a particular high risk speed restriction. One well known example was the former CP-WEST PITT interlocking on the Conrail Pittsburgh Line that retained its 15mph Slow Speed routes due to a sharp curve west of the Pittsburgh Station. Even after the interlocking was removed westbound trains still encounter an Approach Slow at CP-PITT or CP-EAST PITT before the MP353 automatic displaying Clear.
|Signaled speed restrictions are certainly more expensive than signs or ink.|
|1920's technology is sufficient to alert a drowsy Engineer.|
* BAY Interlocking near Baltimore for southbound trains.
* Frankford Junction Curve outside Philadelphia for southbound trains.
* Elizabeth, NJ S-Curve for northbound trains.
* Boston Back Bay station for northbound trains.
Unlike a rapid transit system with some sort of hard ATC or ATO system where the speed is enforced through the entire restriction, Amtrak's method dropped a Clear (125mph) cab signal to an Approach Medium (45mph) signal and then lifted it after a distance sufficient for the Engineer to apply a brake application sufficient to suppress the Automatic Train Control system.
While other eastern commuter railroads such as SEPTA and NJT have installed similar "speed control" cab signal drops on their territories, Amtrak's did the best at getting the train to slow without sufficiently gumming up the works. For example SEPTA now has extensive cab signal speed enforcement in the area of JENKIN interlocking that goes beyond what is required by timetable speeds and NJT recently re-signaled the approach to the Delair Bridge with a non-conditional Approach Limited at the new JORDAN interlocking replacing what had been Clear signals all the way across the bridge and hitting trains with a 2-mile 45mph slow zone.
Anyway the real reason I brought this up was because I actually found a sweet video on YouTube showing a Metroliner cab car as it runs at the front of a Keystone train from Linden, NJ through the Elizabeth S-Curve. You can watch the cab signal drop about 50 seconds into the video and then pop back up about 30 seconds later before the train even gets within sight of the curve. Still, the speed has been slowed and the Engineer still has sufficient operational leeway to not lose time.
There is no reason that Metro North should not have adopted this practice sometime in the last 20 years for the clearly high risk speed restriction at Spuyten Duyvil. The northern limits of CP-12 are 0.7 miles from the curve and the southern limits 0.2 miles. A non-conditional cab signal between those two points would have provided ample warning to any drowsy engineer with room to bring the train to a complete stop if necessary. I am sure MNRR will apply this "solution" both at the Spuyten Duyvil curve (and, I assume, the similar curve at New Rochelle) in advance of whenever they complete their PTC project, but keep in mind that the PTC project that will cost 300-500 million dollars on Metro-North alone would have been just as effective as the existing ATC technology if used properly. Why pay more?