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, 1/10/1979, as amended at 48 FR 6123, 2/10/1983