But the relations to the investors cover but a small part either of the work or of the responsibility of the railroad authorities. They are managing not merely a piece of property, but a vast and complicated organization of men, and an instrument of public service. In all these capacities their cares are equally great. The operating and the traffic departments are not less important than the financial department. The relations of the railroad to its employees, and to the business community at large, are even more perplexing than its relations to the investors. Of the questions arising between the railroad and its employees we are just beginning to realize the full importance. They are not matters to be settled by private agreement or private war. If they involve a serious interruption of the business of the community they concern public interests most vitally. The community cannot afford to have its business interrupted by railroad strikes. On the other hand, it cannot allow the men to make this public duty of the railroads a means of enforcing their own will on every occasion, to the detriment of all discipline and responsibility, or in disregard of investors' rights. How to compromise between these two conflicting requirements is one of the most serious problems of the immediate future.[29] Little progress in this direction has as yet been made, or even systematically attempted. The questions arising from the relations of the railroads to those who use them are wider and older. From the very outset attempts were made to regulate railroad charges by law in various ways. The fear at that time was that they might be made unreasonably high. This fear proved groundless. From the outset the rates were rather lower than had been expected, and much lower than by many of the means of transportation which railroads superseded. These low rates caused a great development in business; and this, in turn, gave a chance for such economy in handling it that rates went still lower. Each new invention rendered it easier to do a large business at cheap rates. The substitution of steel rails for iron, which began shortly after the close of the war, had an enormous influence in this respect. This was not merely due to the direct saving in repairs, which, though appreciable, was moderate in amount. It was due still more to improvements in transportation which followed. It was found that steel rails would bear heavier rolling-stock. Instead of building ten-ton cars to carry ten tons of cargo, companies built twelve-ton cars to carry twenty tons of cargo, or fourteen-ton cars to carry thirty tons; and they made the locomotives heavy enough to handle correspondingly larger trains. A given amount of fuel was made to haul more weight; and of the weight thus hauled, the freight formed a constantly increasing proportion as compared with the rolling-stock itself. The system of rates was adopted to meet the new requirements. Charges were