(a) Where signs or markings are in place to define a no- passing zone, no driver may at any time drive on the left side of the roadway within the no-passing zone or on the left side of any pavement striping designed to mark such no- passing zone throughout its length except as otherwise indicated in this Section.
(b) The pavement striping designed to mark the no-passing zone may be crossed (1) from the left-hand lane for the purpose of completing a pass that was begun prior to the beginning of the zone in the driver's direction of travel, (2) from the right-hand lane when making a left turn into or from an alley, private road or driveway when such movement can be made with safety or, (3) under conditions set forth in Section 22-26 (a) 2 of this Chapter.
(M.C. 1963, § 20.318.)