IMPACT TRAIN SPEED HAS ON LINE CAPACITY OF A SINGLE TRACK IMPACT TRAIN SPEED HAS ON LINE CAPACITY OF A SINGLE TRACK GRADES. As a train negotiates a grade the amount of motive power required to move the train over the grade increases. When grades are encountered the railroad normally takes one of three options. Additional motive power can be added to the train permitting faster train speeds over the grade. The second option involves letting the train operate at lower speeds over the grade. The last option is a compromise between the first two, whereby the railroad may increase motive power assigned to the train, but lets the train negotiate the grade at a reasonable speed. In this study the grades of the major north south rail routes have been examined. Although some routes have ruling grades of one percent, other railroads have more favorable grades of under 1/2 of one percent (0.50). In this study locomotive assignments are based on an average speed of 20 mph or a 1/2 of a percent grade. TRACK CONDITIONS. The condition of railroad track has a direct influence on line capacity. United States railroads are subject to track safety standards developed under the Federal Railroad Safety Act of 1970. Under these safety standards six classes of track are authorized with each class being Each segment of rail line assigned an operating speed limit. Most of the railroad routes examined in this study are mainlines having a minimum of 118 pound rail and are maintained to Class 4 FRA track standards. Although most railroads have some segment of Class 1, 2 & 3 tracks, their lines maintained to lower standards are usually confined to secondary branch lines. YARDS AND SERVICING FACILITIES. The efficient operations of trains require that the necessary locomotive refueling and car inspection facilities be built and maintained. During recent years many railroads have abandoned the older practice of building major yards at crew change points to perform this servicing function. The current practice is to build locomotive refueling and car inspection facilities along the carriers' main line tracks permitting the train to avoid a major yard unless car classification work is required. 43 EVALUATION OF FACTORS INFLUENCING CAPACITY Railroad capacity is significant in terms of revenue freight transported. In total, more than 11 elements can be identified which influence line capacity. If any one of these elements is adjusted a change in rail line capacity can be expected. A comprehensive approach to railroad capacity should reflect the dynamic interrelationships associated with these various elements. During the last twenty years numerous business decisions have been made which directly influence railroad capacity. Most of these decisions were made to improve the competitive position of the railroads and it is highly probable that the increased capacity was not seriously considered when making the decision. Nevertheless, the direct effect of these decisions has been increased rail capacity. The development of the 89 ft. auto rack and trailer on flat car equipment during the late 1950's has forced many railroads to extend the length of sidings to accommodate longer cars The railroads have been retiring the older 50 and 70 ton cars and replacing them with 100 ton cars. Purchasing of 100 NT rail |