Delaware Code Title 21. Motor Vehicles § 4117. When overtaking on the right is permitted

(a) The driver of a vehicle may overtake and pass upon the right of another vehicle only under conditions permitting such movement in safety.  In no event, except as permitted in subsection (c) and (d) of this section, shall such movement be made by driving off the roadway, main traveled portion, or regular moving traffic lane of the highway.

(b) Overtaking and passing on the right, except as permitted herein, shall be unlawful:

(c) When the vehicle overtaken is making or about to make a left turn, the vehicle approaching from the rear may pass on the right using the shoulder if necessary.

(d) When the overtaking vehicle is a Delaware Department of Transportation authorized vehicle or an emergency vehicle, as defined in § 4106(e) of this title, responding to an emergency, the overtaking vehicle may pass on the right using the shoulder if necessary.