As it's name implies the Vehicle Pad constructs vehicles for your team. Vehicles can be purchased by any player with credits earned in a match. Currently in Tribes: Ascend every Capture-the-Flag map has a vehicle pad. The pad is powered by the team's Generator and will go offline if it is destroyed.
The Vehicle Pad produces the following vehicles (prices as of patch 1.0.961.0):
When a player purchases a vehicle they will be teleported inside it once it has been completed. If the player exits the vehicle after purchasing it any other player on either team can take control of it.