21 Del. C. § 4311A: Muffler requirements for commercial vehicles equipped with engine compression brake devices.

(a) No person shall drive a commercial vehicle equipped with an engine compression brake device on a highway, including residential streets, unless such commercial vehicle is also equipped with a muffler in good working order and in accordance with manufacturer’s specifications and in constant operation to prevent excessive noise.

(b) For the purposes of this section, “engine compression brake device” shall mean any device that uses the engine and transmission to impede the forward motion of the motor vehicle by compression of the engine.