Change List for this Rule


General Order 95


Section VII


Detailed Construction Requirements for Trolley and Electric Railway
Contact and Feeder Conductors and Their Supporting Messengers,
Span Wires, Etc. (Class T Circuits)


74.4    Clearances

Except where specifically designated, Class T conductors take clearances specified for supply lines of like voltage.


A.    Above Ground

The minimum vertical clearances above ground for Class T conductors shall be those specified in Rule 37 , Table 1 . References to rules modifying the tabulated values for supply conductors and Class T conductors of equal voltage are given in notes following Table 1 .


B.    Above Railways


(1)    Tracks:  The vertical clearance of 22.5 feet above rails for trolley contact, feeder and span wires of Table 1, Case 2, Column C, may be decreased to 19 feet where the railway involved does not transport nor proposes to transport freight cars.


Note:    Revised February 1, 1948 by Supplement No. 1 (Decision No. 41134, Case No. 4324) and Revised January 13, 2006 by Decision No. 05-01-030


(2)    At Grade Crossings of Railroads: Unless electric railroad systems are protected by interlocking plant at grade crossings with interurban or other heavy or high speed railway systems, the trolley contact conductors shall be at the same elevation above their own tracks throughout the crossing and next adjoining spans. In addition to the above, catenary construction shall be provided when crossing spans exceed 100 feet (see Figure 74–2 ). This rule is not intended to apply where pantograph collector or similar device is used.


Note:    Revised October 9, 1996 by Resolution SU–40.


C.    Between Conductors

The minimum clearances specified in
Case 2, Column D; Case 4, Column B; Case 5, Column E and Case 15, Column D of Table 2 are not required between Class T conductors of the same potential and system.

The minimum clearance of 24 inches specified in
Table 2, Case 9, Column D , is not required between trolley feeders of the same system provided, however, that the clearance shall be not less than 12 inches.

The minimum clearance of 48 inches specified in
Table 2, Case 2, Column D, and Case 4, Column B is not required in double trolley construction between feeder auxiliary span cables or equalizer cables and trolley contact conductors of opposite polarity provided, however, that the clearance shall be not less than 18 inches or, where the feeder or equalizer cables are attached to the span wires in accordance with Rule 74.4–G3 , the clearance shall be not less then 3 inches at the point of crossing the trolley contact conductor.

Trolley contact conductors of the same system but of opposite polarity, (as in double trolley construction) or of different systems and of the same or opposite polarity, shall have a separation of not less than 11–1/2 inches. Excepted from this provision are conductors at switches, frogs, crossings, etc., in which locations a vertical separation of not less than 3 inches shall be maintained between conductors of opposite polarity.


D.    From Poles

Class T conductors of not more than 750 volts and of the same polarity, potential and system which are carried on poles supporting no other conductors are not required to obtain the clearance of 15 inches from center line of pole (
Table 1, Case 8 ), but shall comply with the clearance of 3 inches from surface of pole (Table 1, Case 9 ). The attachment of clearance arms for either supply or communication service drops does not affect the pole clearance of Class T conductors which are carried on one side or the top of a pole.

Where Class T conductors are carried on more than one side of jointly occupied poles the clearances of
Table 1, Cases 8 and 9 , shall apply and a climbing space conforming to Rule 54.7 shall be provided.

Class T conductors of not more than 750 volts passing unattached shall clear nonclimbable street lighting and traffic signal poles, or standards, including mastarms, brackets, and lighting fixtures; a radial distance of 15 inches as specified in
Table 1, Case 10, Column C ; except when the conductors are mechanically protected from abrasion by materials specified in Rule 22.8 . Such mechanical protection shall extend 15 inches in each direction along the cable from centerline of pole, standard, attaching mastarms, or fixtures; whether passing above, below or alongside. The conductors shall be installed in such a manner so as not to interfere with light distribution from lighting fixtures and shall not hamper workmen changing lamps or maintaining equipment.


Note:    Modified January 8, 1980 by Decision No. 91186.


E.    Under Bridges, Etc.

A reduction of the clearances given in
Table 1 to a minimum of 14 feet for trolley contact conductors is permitted for subways, tunnels or bridges, and for 0 - 750 volt conductors within exclusive and semi–exclusive rights–of–way as defined by Alignment Classification 9.04–a. and 9.04–b.(1) contained in General Order No. 143–A , “Safety Rules and Regulations Governing Light–Rail Transit”, provided the railway does not operate freight cars where the vertical distance from the top of car or load to trolley contact conductor is less than 6 feet. This will require the grading of the trolley contact conductor from the prescribed construction down to the reduced elevation (see Figure 74–1 ).

No clearance is specified between the trolley contact conductor and the structure. Where the structure is of material which will ground the trolley current in the event the collector leaves the contact conductor, a properly insulated trolley trough or equivalent protection shall be installed to prevent contact between the collector and the structure. Where pantograph collectors are used, this protection is not required. See
Rule 54.4–I for provisions applicable to conductors other than trolley contact conductors.


Note:    Modified June 27, 1978 by Decision No. 89022; and January 21, 1992 by Resolution SU–10.


F.    At Points of Failure


(1)    Overhead Trolley Contact Conductors: All overhead trolley contact conductors shall be so supported and arranged that the breaking of a single “suspension” or fastening will not allow the trolley conductor, or live span wire, or current carrying connections to come within 10 feet from the ground or from any platform accessible to the general public. This does not apply to feeder taps to or from trolley contact conductors (see Appendix G, Figs. 65 and 66 ).


(2)    Trolley Contact Conductors of More than 1,500 Volts: Where in urban districts and not on fenced rights–of–way, trolley contact conductors of more than 1,500 volts shall be so suspended that if the conductor is broken at a single point it cannot fall within 10 feet from the ground or from any platform accessible to the general public. This practically requires catenary construction.


G.    From Span Wires, Guys and Messengers

The minimum clearances of conductors from span wires, guys and messengers are specified in
Table 2 and are modified for Class T conductors by the following rules and by Rule 78 .


(1)    Span Wires and Contact Conductors: The minimum clearance of 48 inches specified in Table 2, Case 1, Column B, and Case 2, Column A , is not required between span wires and trolley contact conductors supported therefrom.


(2)    Trolley Contact Conductors of 750 - 7,500 Volts: The clearance specified in Table 2, Case 1, Column E, and Case 5, Column A , shall be increased to not less than 48 inches where trolley contact conductors of 750 - 7,500 volts are involved. These clearances are not intended to apply to span wires and trolley contact conductors supported therefrom.


(3)    Feeder and Equalizer Cables: Feeder auxiliary span cables or equalizer cables shall be installed at a distance not less than 18 inches above the span wire (see Appendix G, Figure 67 ), or in lieu thereof, such cables, when protected by the equivalent of triple–braid weatherproof covering, may be supported not less than 2–1/2 inches above the span wire by insulating supports attached to the span wire at intervals of not more than 5 feet.