(a) The Department of Transportation is authorized to determine those portions of any highway where overtaking and passing or driving to the left of the roadway would be especially hazardous and may by appropriate signs or markings on the roadway indicate the beginning and end of such zones and when such signs or markings are in place and clearly visible to an ordinarily observant person, every driver of a vehicle shall obey the directions thereof.

(b) Where signs or markings are in place to define a no-passing zone, no driver shall at any time drive on the left side of the roadway within such no-passing zone or on the left side of any pavement striping designed to mark such no-passing zone throughout its length; except as follows:

(1) When reasonably necessary to avoid parked vehicles, pedestrians, animals, surface hazards or other obstructions on a roadway and where only 1 travel lane proceeding in a given direction exists but while still obeying the limitations described in §§ 4118 and 4119 of this title;

(2) When reasonably necessary to pass a vehicle or bicycle proceeding at less than the normal speed of traffic at the time and place and under the conditions then existing and where only 1 travel lane proceeding in a given direction exists but while still obeying the limitations described in §§ 4118 and 4119 of this title; or

(3) When making a left turn into or from an alley, private road, driveway or highway.

21 Del. C. 1953, § 4120; 54 Del. Laws, c. 160, § 1; 57 Del. Laws, c. 670, § 13A; 60 Del. Laws, c. 701, §§ 19, 20; 81 Del. Laws, c. 196, § 1.