The reason behind big fleets wanting full automatic is 4 fold , 1st is driver training , its easier and cheaper to simply train drivers on auto boxes , 2nd is ride quality , auto boxes give a smoother (and slower) run up the gears so the bus feels smoother to passengers when its on the move , 3rd is maintainance , in an automatic the gearbox when damaged or defective can simply be unbolted and swapped for another unit in minimal time , and 4th is safety , tests show that with automatic gearboxes the driver spends less attention focused on the operation of the vehicle controls and more time focused on the road enviroment , the estimate is that auto boxes reduce accident risk by nearly 60% (most accidents in PSV's are caused by human error)