D.C. Code § 50-1108: "Motor vehicle" defined.

As used in this subchapter, the term "motor vehicle" means all vehicles propelled by internal-combustion engines, electricity, or steam. The term "motor vehicle" shall not include traction engines, road rollers, vehicles propelled only upon rails or tracks, personal mobility devices, as the term is defined in § 50-2201.02(13), electric mobility devices, as the term is defined in § 50-2201.02(6A), motorized bicycles, as the term is defined in § 50-2201.02(11A), or a battery-operated wheelchair when operated by a person with a disability.