Status of N&W Signals & Interlockings as of Jan 1, 1914

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>From Signal Engineer, vol 7, no. 6, June 1914, page 169 ff. 


INTERLOCKING PLANT STATISTICS: 
============================== 
Mechanical Interlockings - 41 
Electro-Mechanical Interlockings - 3 
Pneumatic Interlockings - 0 
Electro-Pneumatic - 1 
Electric Interlockings - 11 
TOTAL Number of Interlockings, All Types - 56 

# Working Levers - 1224 
# High Interlocking Signals - 480 
...... # Disc Signals - 0 
...... # Light Signals - 0 
# Dwarf Signals - 281 
...... Disc type - 0 
...... Light type - 0 
Other Type Signals - 4 
Upper Quadrant Interlocking Signals - 204 
Lower Quadrant Interlocking Signals - 555 
# 3 Position Signals - 0 
# 2 Position Signals - 689 
# Switches - 336 
# Derails - 265 

COLOR OF NIGHT INDICATIONS: 
Stop - Red 
Caution - Green 
Clear - White 

INTERLOCKING SIGNAL ILLUMINATION: 
# of plants using oil lamps -54 
# of plants using gas lamps - 0 
# of plants using electric lamps - 0 

CIRCUITS: 
# of interlocking plants using DC track circuits - 3 
# of interlocking plants using AC track circuits - 38 
# of plants using DC switch & signal circuits - 4 
# of plants using AC switch & signal circuits - 39 
# of plants with Approach Locking - 24 
# of plants with Time Locking - 17 
# of plants with Route Locking - 0 
# of plants with Detector Circuits - 0 
# of plants with Facing Point Locks - 0 
# of plants with Bolt Locks - 2 
# of plants with Detector Bars - 55 
# of plants with Switch & Lock Movements - 0 
# of Hand Thrown Switches within Interlocking Limits Controlled from Towers - 3 
# of Hand Thrown Switches within Interlocking Limits NOT Controlled from Tower - 4 
# of outlying switches controlled from towers - 2 

AUTOMATIC BLOCK SIGNAL STATISTICS: 
=================================== 
Miles of Single Track Automatic Block Signaled - 101.1 
Miles of Double Track Automatic Block Signaled - 461.8 
Miles of Third & 4th Track Automatic Block Signaled - 0 
Total Miles of Automatic Block Road - 562.8 
Total Miles of Automatic Block Track - 1024.6 


NON-AUTOMATIC BLOCK STATISTICS: 
================================ 
Miles of Single Track non-ABS - 1051.2 
Miles of Double, 3rd & 4th Track non-ABS - 0 
Total Miles of Road non-ABS - 1051.2 
Total Miles of Track non-ABS - 1051.2 

TOTAL AUTOMATIC BLOCK and Non-AUTOMATIC BLOCK: 
================================================ 
# of Miles of Road -1614.0 
# of Miles of Track - 2075.8 

TOTAL PASSENGER LINES OPERATED: 
================================ 
Miles of Road - 1743.3 
Miles of Track - 2205.1 

PERCENTAGE OF MAIN TRACK MILES BLOCK SIGNALED (either ABS or non-ABS): 93.8% 
================================================================== 

Some observations: On a track mile basis, about half the N&W was ABS and about half was operated by Manual Block. By deduction, it appears that about 333 miles of N&W's main track was operated by Time Table and Train Order method only, without either MBS or ABS. N&W was still using Green for Caution and White for Clear. There was one EP (electro-pneumatic) interlocking in service... one wonders where it was located. In its manual interlockings, N&W was committed to the old Detector Bars and was not using Facing Point Locks. Thirty-nine of N&W's 41 interlockings had AC (instead of DC) track circuits and/or switch and signal circuits, which lines up nicely with N&W's later commitment to AC track circuits for block signaling. The Switch & Lock movement had not yet made its advent on the N&W. Twenty-six percent of N&W's interlockings (15 out of 56) were of some improved version (electro-mechanical, electro-pneumatic or electric) rather than mechanical. Forty-three percent of N&W's home signals were of the newer Upper Quadrant type by this time. 

Questions yet to be answered: (1) Where was the N&W's first on-line interlocking? ("HJ" at Hagerstown Jct, sometimes termed "N&W's first interlocking," was a PRR facility, although the N&W ran through it.) (2) When did N&W change from Green for Caution and White for Clear, to Yellow for Caution and green for Clear? (3) What was the genesis of N&W's involvement with AC for track circuits and interlocking control? 

Presently, it appears that the only years of Signal Engineer (and its successor, Railway Signal Engineer) to have been digitized are 1908, 1909, 1911, 1913, 1914, 1915, 1917, 1918, 1919, 1920 and 1921. As soon as the complete series becomes available, a more coherent picture of N&W's interlocking and signaling history may be possible. What a whopping Excel spreadsheet could be made from 30 or so years worth of these annual statistics! 

-- abram burnett