Oddly enough, there is none. There's no such thing as "all vehicle" in the way that there is "all player object" (Armor::onTrigger).
You have to package TWO onImpact functions: WheeledVehicleData::onImpact(%data, %obj, %col, %pos, %speed) and FlyingVehicleData::onImpact(%data, %obj, %col, %pos, %speed).
One would assume that a VehicleData would exist from the naming conventions that exist, but it does not - and indeed, there is also no such thing as a Vehicle.