make normal car but just disable it and add output from them the point to activate the cart.
func_train or whatever entity you use probaly has option "start disable?" set to yes and then go to point trigger and add in output
"OnTeamCap1 > (cart name) > enable"
if you cart doesnt move then first learn how to make movable objects.
if you mean by cart something like train (automaticaly movable object without pushing) then just make the object and almost same output on point but "SetSpeed" or something like that. then you need to write bel ow the setspeed the speed. should looks something like that:
My output named: OnTeamCap1 <--- when activates
Tragets entities named: ExambleTrain <--- entity name
Via This Imput: SetSpeed <--- what to do
With a Parameter Override of: 100 <--- others (here you setting the speed)