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Discussion relating to the PRR, up to 1968. Visit the PRR Technical & Historical Society for more information.
 #1077902  by Lackawanna565
 
Been wondering for awhile why they didn't have a slow clear aspect on the big position light signals. I know with using slow approach in cab signal territory the cab signal will up grade itself to clear. And also. How come they never had approach limited and limited clear on the pedestal signals?
 #1077991  by ThirdRail7
 
Lackawanna565 wrote:Been wondering for awhile why they didn't have a slow clear aspect on the big position light signals. I know with using slow approach in cab signal territory the cab signal will up grade itself to clear. And also. How come they never had approach limited and limited clear on the pedestal signals?
Answer your own question by thinking about this: When is the last time you saw a 3 headed PRR or former signal mast?

As for the limited aspects, that speed came later in life. They weren't wired for such even on the high signals. Before they changed the codes and signals, they had a funny looking triangle hanging next to the signal to indicate a limited spedd upgrade! They were all over the place.

So, I'm thinking medium speed was the best they had when the pedestals were installed.
 #1078042  by westernfalls
 
In a perfectly thought out world, maybe the PRR would have had slow clear on a high signal mast; but then they probably wouldn't have had position light signals at all.

The medium clear and slow approach interlocking signals sufficed to get trains through an interlocking at the correct speed. The cab signal, or a block signal at the other end of the interlocking, could speed things up if the blocks ahead were clear. The golden triangle worked well if all the switches were ok for the higher speed, but the default was slow approach. Flashing aspects fine-tuned things a little better, but there still was no slow clear.

Pedestal signals were used in slow speed locations. The difference between medium and limited speed would make no difference so triangles and flashing lights were moot.
 #1078046  by Statkowski
 
Slow Clear is quite possibly somewhat of a rarity on multiple railroads. For example, rarely on the New Haven Railroad did one find signals capable of displaying Slow Clear, the main exception being New Haven Union Station. Coming out of a yard, or a siding, one would normally get Restricting. Of course, by the time the rear of the train was clear of the slow speed trackage, the front of the train was approaching a signal capable of giving less restricting indications, such as Clear. At this point the engineer could crack open the throttle.
 #1078075  by ThirdRail7
 
westernfalls wrote: Pedestal signals were used in slow speed locations. The difference between medium and limited speed would make no difference so triangles and flashing lights were moot.
Weren't dwarfs used in slow speed locations and pedestals used in limited clearance areas where the large position lights wouldn't fit?
 #1078163  by westernfalls
 
ThirdRail7 wrote:
Weren't dwarfs used in slow speed locations and pedestals used in limited clearance areas where the large position lights wouldn't fit?
Perhaps I should have said: Pedestal signals were used in slower speed locations.

It's a matter of visibility and sighting distance. Of course, that's the challenge: Find some that were used where the authorized speed in approach thereto exceeded, say, 30MPH!
Indeed, the pedestals were a brilliant idea for a clearance problem, but so were the "condensed" high position lights at Newark (and later, Harold) and that odd signal on the bridge at Sunbury.
Railway signalling is full of compromises and brilliant ideas.
 #1078604  by Statkowski
 
And for every "rule" there will be an exception, somewhere. And then you'll have the unwritten rules, not found in the Book of Rules or in the back of the Employee's Timetable.
 #1078667  by urrengr2003
 
Have a problem with the previous post; background is 38 years in engine service as both a contract employee and supervisor. There can be no execptions to the carriers written operating rules or personal inturpertations with out seriously compromising the safety and intergrity of the train operation. Rules are written to overlap and make it necessary that more than one responsible individual is involved in their compliance. For example: before I can take a train past a Stop Signal I will of had to violate the provisions of an Approach Signal. All the while this is occuring other members of the crew will of had to violate the provisions of the rules that mandate if I fail to properly control the train they must take action to ensure safety. Thus to get by the stop signal I and other members of the crew would have violated several rules before the incident occured. Granted, I would like to have had 1/10 of the monies the carriers spent over the years to make crew members on the rear of trains jointly responsible with those on locomotives, the fact remains that the rules apply equally to all.

The only way one can accept the provisions of a Clearance Form 'A', proceed signal, track warrant, or verbal permission is to have absolute confidance in the fact that others are not inturperting the rules any differently and that there is no execption or unwritten rule that governs.

Been retired now for 10+ years so perspective may be a little hazy in a world where all manner of rules & order is questioned; certanily hope this attitude is not reflected by the operating employees of todays modern carriers. This is why I have such a great difficulty understanding regulatory agencies permitting one man train operations but that's not the subject of this post. Just know from experience the safety net that is provided when another member of a crew "calls" signal indications by name on a moving train at 4AM when the crew has been on duty since yesterday afternoon.
 #1079136  by ExCon90
 
westernfalls wrote:
ThirdRail7 wrote:
Weren't dwarfs used in slow speed locations and pedestals used in limited clearance areas where the large position lights wouldn't fit?
Perhaps I should have said: Pedestal signals were used in slower speed locations.

It's a matter of visibility and sighting distance. Of course, that's the challenge: Find some that were used where the authorized speed in approach thereto exceeded, say, 30MPH!
Indeed, the pedestals were a brilliant idea for a clearance problem, but so were the "condensed" high position lights at Newark (and later, Harold) and that odd signal on the bridge at Sunbury.
Railway signalling is full of compromises and brilliant ideas.
Yes, I was told by a signal engineer that PRR policy was not to use pedestal signals where speed exceeded 30 mph. I remember that the westward home signal at PITT presented a problem because all signals in the interlocking were slow-speed dwarfs, so the best indication that could be displayed was Slow Clear. To provide greater visibility, considering the location, the dwarf was mounted all by its lonesome on a signal bridge spanning all tracks.