General Order 64-A
Detailed Construction Requirements For Trolley Lines
(Class T Circuits)
Messengers which are grounded may be attached directly to the supporting poles or structures at a lesser clearance than specified in Table 1, Cases 7 and 9. Where so installed at a distance less than 6 feet below open wire supply conductors of other circuits, such messengers shall be protected by a guard arm at least 4 feet in length placed as close to them and as nearly parallel with them as practicable. In lieu of the guard arm suitable insulating covering of the length specified may be placed around the messenger. Where dead-ended or wrapped around a pole for any reason, they shall be at least 6 feet vertically below supply conductors. Should it be impracticable to maintain such vertical clearance, a reduction to 4 feet below supply conductors of 0-750 volts will be permitted, provided the messenger is suitably guarded with the equivalent of double guard arms placed directly above it and substantially parallel with it.