here is the tutorial http://hce.halomaps.org/index.cfm?fid=2298
make all of this that you need, then go into sapien and go to mission ai and make your encounter, then go to command lists and make a new one, name it something you can easily remember like "car" and open that new tag, go to commands and make a new one, make this a vehicle command and set it to "driver", make the vehicle distance about 30 world units and place the vehicle beside the ai's spawn point, go to (ai\encounters) and to your encounter then (squads) your squad and (starting locations) in there under the property view you'll see command lists set it to car, save and make your map, so thats it and you should know that the ai don't really want to drive in a strait line