The Unreal Tournament 2004 Preview on IGN offers a detailed look at some of the maps in the upcoming UT 2003 sequel. In addition, they also offer a look at the gameplay modes on tap, including the following on the role of the newly added vehicles:

But even though some of the maps seem too large to accommodate smaller groups of players, the team behind the game have come up with an intriguing solution in a new team-based mode called Onslaught. This large-scale, vehicle-focused game concentrates and focuses the action so that 12 players can have as much fun as 32. Each team has a power core that they need to protect. Between the teams' power cores a number of smaller power nodes are scattered across the map. Each node is linked to one or more other nodes between the two team-owned nodes.