The volume of traffic is the chief factor in establishing rates, either regular or special. It is an especially important factor in establishing a commodity rate. In a given community, some one commodity may be produced in large quantities. Perhaps it is a raw material which must be transported to certain manufacturing centers. To encourage the development of the industry, thereby creating a large volume of traffic, the railroads leading from the point where the traffic originates establish a commodity rate to other points, where the raw material can be used to advantage by the manufacturer. Or, perhaps, important manufacturers are located on other roads, in which case connecting lines join with the originating road and issue what is known as a _joint tariff_. This enables the producer to deliver his raw material to the manufacturer on favorable terms, when to pay class rates might compel him to abandon the enterprise, with a consequent loss of traffic to the railroads. This discriminates against no one, since every shipper of the particular commodity between the points named is entitled to the special commodity rate. Frequently, however, a commodity rate exists between certain points which might, under certain conditions, be taken advantage of by a shipper located at a point outside of those named in the commodity tariff. For illustration, a manufacturer in Peoria, Illinois, is shipping a commodity on which a special rate is granted between Chicago and Milwaukee, but takes a class rate from the point of shipment. He makes a shipment to Milwaukee and pays the through class rate provided from the point of shipment, when by proper billing he would have paid the class rate to Chicago, and secured the benefit of the commodity rate from that point to Milwaukee. A lack of knowledge of commodity rates in effect in the manufacturer's territory has resulted in an unnecessary expense--a loss of money. The claim might be made that the billing clerk at the local freight office should have given the shipper the benefit of the lowest rate. But he will fall back on the classification and be prepared to show that he has given the only rate quoted on shipments from Peoria to Milwaukee, which is the class rate. It is no part of his duties to keep posted on commodity rates granted by another road, while it is distinctly to the interest of the manufacturer to know of the existence of all such rates applying to his product. =Freight Tariffs.= The Interstate Commerce Act provides that two copies of every freight tariff issued by the railroads shall be placed on file at each freight office, for the inspection of the public. Since the rates must be made public, the railroads do not object to supplying shippers with copies of the tariffs applying to their product. Through the local freight agent, copies of all tariffs applying from the point of shipment can be obtained.