In addition to warnings by whistle, bell or horn as required by statute, every railroad train shall give warning by prolonged or repeated whistling when passing or meeting or about to pass or meet a train, at or in the immediate vicinity of a grade crossing, under such circumstances that the second train will materially obscure the view of the first mentioned train to persons who may be about to use the crossing.
Ill. Admin. Code tit. 92, § 1535.502
Amended at 11 Ill. Reg. 19027, effective November 15, 1987