§21–1131.

    (a)    Except as provided in subsection (b) of this section, a person may not knowingly or intentionally cause a diesel–powered motor vehicle to discharge clearly visible smoke, soot, or other exhaust emissions onto another person or motor vehicle.

    (b)    This section does not apply to a person operating:

        (1)    A diesel–powered vehicle that discharges visible exhaust as the result of normal acceleration or towing;

        (2)    A commercial vehicle with a gross weight of 10,000 pounds or more; or

        (3)    A construction vehicle operating at a construction site.