Urban Assault Vehicles are large armoured
military vehicles. Somewhat similar in purpose to
Infantry Fighting Vehicles, the role of the
UAV is to provide an armoured, armed unit suitable for
close quarters combat in a city or other
developed area. They are also referred to as
Interim Armored Vehicles and
Land Assault Vehicles, among other things.
Halfway between an APC and a jeep, the UAV can be best imagined as a successor to the half-track trucks of the Second World War. A UAV will typically sport weapons suitable for engaging infantry and soft targets like trucks and lightly armoured vehicles like scout cars, and have rubber tired wheels instead of caterpillar tracks. The result is a swift, relatively quiet, manueverable vehicle to support soldiers in urban combat. It must also be able to withstand support weapons like RPGs which would destroy a HMMWV or other small vehicle.
The advantages over a comparable IFV like the M2 Bradley or BMP2 are numerous. First, the UAV is far swifter on paved roads. Secondly, it's much lighter and less likely to damage the road, a problem Israel has with their behemoth Merkava tanks. It can also keep up with convoys of trucks and serve as an escort. Finally, the vehicle provides a template for modifications for multiple roles in the same manner of an IFV, such as into a cargo or ambulance vehicle.
The M11xx Stryker is an example of a UAV. It has eight wheels, a mounted turret and can carry nine soldiers. During battle, the soldiers disembark and advance, while the UAV follows and provides supporting fire.
Contrary to what the Grand Theft Auto series tells us, the Rhino 'tank' featured in GTA3 and Vice City is actually a UAV, as it has large wheels intead of treads. The Rhino in San Andreas is a M1A1 Abrams tank, but the game engine doesn't seem able to model tank treads.
UPDATE 01/03/2005: I've realized that 'UAV' is also the acronym for Unmanned Aerial Vehicle, like the Darkstar. This is probably why urban assault vehicle isn't commonly used.
Sources: http://www.angelfire.com/art/enchanter/vehicles.html
Desert Combat