The Three-Man Chariot is the unique unit for the Hittites. It replaces the Chariot.
Civilopedia Entry
The Hittites were perhaps most famous for waging fast, deadly warfare with their powerful heavy war chariots. The Three-Man Chariot was an improvement over other contemporary chariots in close combat, because it sacrificed speed for stability and "elbow room" with which to fight. At the battle of Kadesh, the Hittites used three-man chariots to closely engage the Egyptian forces; this almost routed the entire Egyptian host.