I draw the opposite conclusions from your facts. The buses aren't running.full. They will be running to accommodate pax who book it. I thik the incremental fuel needed, due the extra weight of the concerned posters family and luggage is lowUnfortunately it's unlikely the bus would be the better environmental choice as they don't run full typically. They also tend to run the air conditioning while waiting to depart. Uber Green is an excellent choice for those looking for an Environmentaly friendly option.