N&W 1915-1916 Signal Statistics

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>From the Railway Signal Engineer, January 1916, vol. 9, no. 1, pages 12 ff. 

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NOTE on ABBREVIATIONS: ST = Single Track. DT = Double Track. LQ/UQ = Lower Quadrant/Upper Quadrant. TDB = See my Note 1 at bottom. 

AUTOMATIC BLOCK SIGNALING COMPLETED 1915: 
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1. Dwight to Webb, 24.6 miles, DT, 66 signals, 3 position UQ, Polar Track Circuits, AC 

2. Church Road to Hebron, 9.5 miles, DT, 24 signals, 3 position UQ, Polar Track Circuits, AC 

3. Burkeville to Elam, 31.8 miles, ST, 68 signals, 3 position UQ, TDB, AC 

4. Dry Branch to Eggleston, 4.7 miles, ST, 6 signals, 3 position UQ, TDB, AC 

5. Ripplemeade to Pearisburg, 7.1 miles, ST, 16 signals, 3 position UQ, TDB, DC 

AUTOMATIC BLOCK SIGNALING UNDER CONSTRUCTION: 
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1. Poe to Jack, 10.1 miles, ST, 22 signals, 2 position LQ, TDB, DC 

2. Jack to Church Road, DT, 18 signals, 3 position UQ, Polar Track Circuits, AC 

AUTOMATIC BLOCK SIGNALING CONTEMPLATED FOR COMING YEAR (1916): 
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1. Burkeville to Pamplin, 36.9 miles, ST, 86 signals, 3 position UQ, TDB, AC 

2. Pepper to Belspring, 3.8 miles, DT, 8 signals, 3 position UQ, Polar Track Circuits, DC 

3. Pembroke to Ripplemeade, 3.1 miles, DT, 8 signals, 3 position UQ, Polar Track Circuits, DC 

INTERLOCKING PLANTS COMPLETED IN 1915: None 
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INTERLOCKING PLANTS UNDER CONSTRUCTION: 
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1. Burkeville, Type: Junction, 15 working levers in 19 lever frame, Electric, AC 

INTERLOCKING PLANTS CONTEMPLATED FOR COMING YEAR (1916): 
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1. Pamplin, Type: Junction, 33 levers in 44 lever frame, Electric, AC 

2. Jack, Type: Junction, 19 levers in 23 lever frame, Electric, AC 

3. Low Grade Tunnel, Type: ST Tunnel, 26 levers in 32 lever frame, Electric, AC [this was "Cowan"] 

4. City Point Jct, Type: Junction. 11 mechanical levers in 23 lever frame, and 6 electric levers in 12 lever frame 

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NOTE 1: "TDB" (for "Traffic Direction Block") was a rudimentary attempt at signal control developed about 1912 by Union Switch & Signal Co. to match General Railway Signal Co's 1911 patented Absolute Permissive Block System (which used stick traffic relays to tubmble down opposing signals.) The literature gives some hint that TDB was first developed for (or at least tried on) streetcar and interurban lines. The TDB system used old Telegraph Gill Selectors, and later the new AP-60 selector, which had been developed by Western Electric for selective ringing on train dispatching circuits, to end controls and indications. TDB was a short-lived experiment because it had no provision for preventing two or more field stations from transmitting simultaneously. At some point the meaning of the letters "TDB" morphed into "Train Dispatching Block." To my knowledge, the definitive article on the TDB system has yet to be written. 

NOTE 2: The above statistics seem to indicate that the N&W was, by 1915, sold on AC Track Circuits. One wonders why they were still installing DC Polar Track Circuits between Pepper and Pearisburg. Perhaps it was because they did not have their own power house to supply AC signal power for this territory. But where did they get the AC for an AC signal system between Dry Branch and Eggleston? That area probably did not get "rural electrification" from the power companies for another decade or two. 

-- abram burnett 




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