Sometimes a bus is required to stay with the passengers while other times it can return back to the bus company.  If you need the bus to stay with your group until the next departure in your itinerary then select "Yes".  If you do NOT need the bus to stay with your group then select "No".  Sometimes it is cheaper to keep the bus with your group even if you don't need it.  If you select "No" the system will compare the options of leaving the bus with your group or returning it to the bus company headquarters and it will choose the lowest priced option.  If the bus does stay with your group for any reason it is your responsibility to arrange and pay for the drivers lodging.