Section 1535.341  Mounting Lamp Units

a)         Lamp units shall be mounted horizontally on 2 foot 6 inch centers. The mountings for the lamp unit shall be provided with means for adjusting the units in both the horizontal and the vertical planes and for positive locking of the adjustments.

b)         The lamp units preferably should be mounted with a minimum clearance of 7 feet above the crown surface of the highway opposite the signal mast. Special conditions, such as a sharp approach grade, may require a variation in the height of lamps but in general the endeavor should be to place these lamps in the best position with respect to the normal line of vision of drivers of approaching vehicles and still maintain reasonable protection against accidental breakage.

(Source:  Amended at 11 Ill. Reg. 19027, effective November 15, 1987)