The army's most common vehicle is the High Mobility Multipurpose Wheeled Vehicle (HMMWV), commonly called the Humvee, which is capable of serving as a cargo/troop carrier, weapons platform, and ambulance, among many other roles. While they operate a wide variety of combat support vehicles, one of the most common types centers on the family of HEMTT vehicles. The M1A2 Abrams is the army's main battle tank, while the M2A3 Bradley is the standard infantry fighting vehicle. Other vehicles include the Stryker, and the M113 armored personnel carrier, and multiple types of Mine Resistant Ambush Protected (MRAP) vehicles.
What is the least common type of combat support vehicles?