Detailed Construction Requirements for Trolley
and Electric Railway
Contact and Feeder Conductors and Their Supporting Messengers,
Span Wires, Etc. (Class T Circuits)
The basic minimum clearance for trolley span wires are specified in Table 1, Column C and in Table 2, Column A. Modifications of these basic clearances are specified in Rules 37 and 38 and by the following provisions:
A. Above Railways
The minimum vertical clearance of 19 feet above rails for trolley span wires (Table 1, Case 2, Column C) applies only to those railways which do not transport or propose to transport freight cars. The minimum clearance shall not be less than 22 feet where the railway involved does transport or propose to transport freight cars.
B. Under Bridges, ETC
A reduction of the clearance given in Table 1 to a clearance of not less than 14 feet above rails is permitted for trolley span wires under bridges, in tunnels, or in subways, provided the railways does not transport freight cars where the vertical distance from the top of car or load to trolley contact conductor is less than 6 feet. The grading of the level of trolley span wires from the basic clearance to this reduced clearance is permitted at approaches to bridges, tunnels, or subways.
C. From Conductors
The clearances of trolley span wires from conductors shall be as specified in Table 2, Column A, except as modified by the provisions of Rules 74.4-G and 78.
D. From Guys or Span Wires
The clearance specified in Table 2, Case, Column A (18 inches) is not required between trolley span wires, backbones, messengers, and similar wires or cables, used to support trolley contact conductors and appurtenances.
E. From Poles and Crossarms
The clearances specified in Table 1, Column C, Cases 8 and 9, are not intended to apply insulated (unenergized) portions of span wires, backbones, messengers, pulloffs and similar equipment at the poles to which they are attached.