Commercial motor vehicle means a motor vehicle or combination of motor vehicles used in commerce to transport passengers or property if the vehicle—

  1. Has a gross combination weight rating or gross combination weight of 11,794 kilograms or more (26,001 pounds or more), whichever is greater, inclusive of a towed unit(s) with a gross vehicle weight rating or gross vehicle weight of more than 4,536 kilograms (10,000 pounds), whichever is greater; or
  2. Has a gross vehicle weight rating or gross vehicle weight of 11,794 or more kilograms (26,001 or more pounds), whichever is greater; or
  3. Is designed to transport 16 or more passengers, including the driver; or
  4. Is of any size and is used in the transportation of materials found to be hazardous for the purposes of the Hazardous Materials Transportation Act (49 U.S.C. 5103(b)) and which require the motor vehicle to be placarded under the Hazardous Materials Regulations (49 CFR part 172, subpart F).