The saving to the railroads from reduction in car mileage that would be possible if it were not obliged to furnish traveling postoffices, but could use the space occupied by racks and other postoffice features by loading additional mail in cars, would be many times the revenue allowed by the railway postal cars. To illustrate: The car mileage of postal cars (changing apartment cars to full cars on basis of length) is 232,180,000 per annum; the ton mileage of mail 484,683,135, or 2.09 tons per car. From figures obtained from the Postoffice Department, average car weights shown on page 59, table "EE," special mail weighing of 1907, it is ascertained that storage mail cars, which, of course, contain no postoffice features, carry an average of 7.04 tons of mail. At this rate the whole mail business could be carried by the movement of 68,844,000 car miles, or 163,336,000 less than actually employed, due to the postoffice features. The total railway postal car pay is only $4,567,366, or only 2.8 cents per additional car mile, whilst the operating expenses chargeable to running these 163,336,000 car miles, of 70 per cent. of the total movement, amount to $67,000,000. But for the postoffice feature, the combined weight of an entire route could many times be handled in a single car such as is used for express instead of several heavy and expensive postoffice cars, whilst often extra cars for storage mail must be added, for which no extra pay is allowed, the cost of running these storage cars also not being included in the computation of cost of service, as no accurate statistics of their number or car mileage are available. In addition to the furnishing of storage cars, although many R. P. O. routes are paid for on a basis of 40 foot cars, it is not economical for the railroads to construct such cars which are not interchangeable with other equipment and which would have to be thrown aside if through growth of traffic larger cars are afterwards required. As a result, full 60-foot R. P. O. cars have for years been furnished on many 40 and 50-foot routes, the railroad getting no credit for this, whilst on many other routes R. P. O. cars have been run in advance of the fixing of R. P. O. pay for them.