(a) Blue signals displayed in accordance with §218.25, 218.27, or 218.29 signify that workers are on, under, or between rolling equipment. When so displayed—

(1) The equipment may not be coupled to;

(2) The equipment may not be moved, except as provided for in §218.29;

(3) Other rolling equipment may not be placed on the same track so as to reduce or block the view of a blue signal, except as provided for in §218.29 (a), (b) and (c); and

(4) Rolling equipment may not pass a displayed blue signal.

(b) Blue signals must be displayed in accordance with §218.25, 218.27, or 218.29 by each craft or group of workers prior to their going on, under, or between rolling equipment and may only be removed by the same craft or group that displayed them.