Del. Code tit. 21 § 4337
Those sections of this chapter which follow immediately, including §§ 4338-4342 of this title, relating to clearance and marker lamps, reflectors and stoplights, shall apply as stated in said sections to vehicles of the type therein enumerated, namely passenger buses, trucks, truck tractors and certain trailers, semitrailers and pole trailers, respectively, when operated upon any highway, and such vehicles shall be equipped as required and all lamp equipment required shall be lighted at times mentioned in § 4331 of this title, except that clearance and side marker lamps need not be lighted on any said vehicle when operated within any municipality where there is sufficient light to render clearly discernible persons and vehicles on the highway at a distance of 500 feet.
21 Del. C. § 4337