At first sight it may appear that nothing more is needed, but any such conclusion would be highly erroneous. If we were to examine the fleet of any large motor omnibus, motor cab, or motor haulage concern, we should almost inevitably find that the vehicles employed were almost all of one make and commonly of one type. If an operating company has in the first instance decided to adopt a particular make of vehicle, and if subsequent improvement in design reduces the efficiency of the original type as compared with others of the market, then the natural move is not to change from one manufacturer to another, but to increase or partially renew the fleet by the purchase of new vehicles of the same make but of a more modern model. The change from the old to the new type does not involve alterations in by any means every part of the mechanism, but only in those parts which have in any way shown themselves capable of improvement. In the event of renewals being required, it is not then necessary to stock an entirely new set of spare parts for all portions of the car, but only to get in spares for those parts, the design of which has been changed and improved. In this way, the necessary stock of spare parts is so far as possible reduced, and the work of maintaining the cars is in a similar degree simplified. Almost every type of motor vehicle has its own peculiarities, and it is evidently easier for a mechanic to undertake the maintenance of a certain number of machines all of one make than to keep in running order a similar number of miscellaneous vehicles varying essentially from one another. Then again, the standardisation of one make is an advantage, because for purposes of maintenance the number of workshop appliances required is reduced to a minimum, and it is possible in some cases to obtain machines specially adapted for turning out in quantity some particular part which figures largely in the maintenance of the fleet. Yet another advantage is that the driver of any one car can, without danger or loss of efficiency, be put on to any other car, if his own is undergoing repair or overhaul, while the work of those departments concerned with the storing and issuing of parts is greatly simplified, and the accommodation required for the efficient operation of the whole concern is reduced. If these arguments apply to an industrial organisation working under normal conditions, they apply still more strongly to a hastily enlarged temporary organisation evolved in time of war. Moreover, in the latter case the unreliable running of a fleet of cars does not represent merely a temporary financial loss or a diminution in prestige. Its result must inevitably be to cause, among the troops behind which the motor column is working, a lack of necessities either in respect of food or of warlike materials. In either case, the result is immeasureable and the consequences may well prove fatal.