Section 218.25 - Workers on a main trackWhen workers are on, under, or between rolling equipment on a main track:
(a) A blue signal must be displayed at each end of the rolling equipment; and(b) If the rolling equipment to be protected includes one or more locomotives, a blue signal must be attached to the controlling locomotive at a location where it is readily visible to the engineman or operator at the controls of that locomotive.(c) When emergency repair work is to be done on, under, or between a locomotive or one or more cars coupled to a locomotive, and blue signals are not available, the engineman or operator must be notified and effective measures must be taken to protect the workers making the repairs.44 FR 2175, Jan. 10, 1979, as amended at 48 FR 6123, Feb. 10, 1983