(1) In case of obstruction,- (a) whenever in consequence of an obstruction of a line, it becomes necessary for a railway servant to stop approaching trains, he shall proceed plainly showing his stop hand signal to a point six hundred meters from the obstruction and place on the line one detonator and then proceed to a point one thousand two hundred meters from the obstruction and place on the line three detonators, about ten meters apart, at such place;
Provided if he sees an approaching train before he is able to protect as above he shall try to apprise the loco pilots of approaching trains about possible infringement of adjacent lines through approved means of communication , if available, and immediately place one detonator as far away from the disabled train or obstruction. If he has already placed one detonator at six hundred meters and not in a position to reach the distance of one thousand two hundred meters, he shall again place one detonator as far away as possible.
Provided further that in case of multiple lines he shall call for assistance, if not already available, through the approved means of communication to depute competent person, if not already available, to place detonators on the line as above, making a beginning from the direction from which the train is most likely to come first.
(b) if the said railway servant is recalled, before the obstruction is removed, he shall leave down three detonators, on his way back, pick up the intermediate detonator.
(2) In case of thick foggy and tempestuous weather impairing visibility.- whenever it is necessary to indicate to the loco pilot of an approaching train the locality of a signal,
(a) two detonators shall be placed on the line, by a railway servant appointed by station master in this behalf, about ten meters apart, and at least two hundred seventy meters outside the first stop signal;
(b) the station working rules shall prescribe the visibility test object from a distance of not less than one hundred eighty meters and can be a post erected for the purpose and lighted at night or light of a fixed colour light signal.
Note: also see rule 220 178 THE GAZETTE OF INDIA : EXTRAORDINARY [PART II—SEC. 3(i)]