Railways – Car yard
Reexamination Certificate
2000-11-21
2002-07-16
Morano, S. Joseph (Department: 3617)
Railways
Car yard
Reexamination Certificate
active
06418854
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to railroads particularly to methods of sorting cars in railroad yards.
DESCRIPTION OF THE RELATED ART
The purpose of sorting railroad cars is to collect them into “blocks” or groups of cars moving together to the next rail terminal, or having commodity, car type or some other attribute in common. Once individual cars have been collected into blocks, the blocks can be assembled into trains. If a train makes any intermediate stops? blocks are usually arranged in order of the sequence of stops, so all intermediate switching can be performed from the front (or occasionally the rear) of the train. Armstrong, J. H. (1998) in
The Railroad: What It Is, What It Does: The Introduction to Railroading
, 4th
Edition
. Simmons-Boardman Books, Omaha. Nebr. offers an excellent introductory text with a section on railroad terminal operations at pp. 197-211.
A railroad “hump yard” utilizes a raised section of track, from which cars are individually cut off, and allowed to roll by gravity into their proper classification tracks. This contrasts with a “flat yard” where railcars are individually shoved into their proper tracks by switch engines. In single stage sorting, only one block is assigned to a track at any point in time. Multiple stage sorting builds more than one block on each track simultaneously. Beckmann, M. J., McGuire C. B. and Winsten C. B. (1956) in
Studies in the Economics of Transportation
. Oxford University Press, London, on pp. 127-171 describe in detail the differences between hump versus flat yards, as well as ways their use can be coordinated to minimize total switching and delay cost. Troup, K. F., ed. (1975) in
Railroad Classification Yard Technology: An Introductory Analysis of Functions and Operations
, Transportation Systems Center, Cambridge, Mass., (DOT-TSC-FRA-7519), NTIS #PB246724, hereinafter Troup (1975), developed a “primer” on railroad yard operations. In general, hump yards are better suited for classification of railcars one-at-a-time, while flat yards may be more efficient for large blocks or “cuts” of cars which remain coupled together during the switching movement.
Very few hump yards have been built in recent years, as railroads have suffered the loss of a large portion of their traffic base to trucking competitors. The clear trend has been towards closing of hump yards rather than building new facilities; in some cases, portions of old facilities remain in use as flat switching yards, as in Russell, Ky., Dewitt, N.Y., and Enola, Pa.; in some cases former hump yards have been converted into intermodal facilities as happened to Norfolk Southern's yards in Atlanta, Ga. and Rutherford, Pa.; sometimes land has been released for non-transportation use, as in Potomac Yard, Va., just a stone's throw away from the U.S. Patent and Trademark Office in Crystal City. Many surviving facilities now operate at close to maximum throughput and under a state of chronic congestion, to the point that they often cannot even accept newly arriving trains, which have to be parked on the main line. Needless to say, this has an extreme adverse effect on railroad service reliability, which in turn has contributed to further loss of traffic to the trucking industry.
Although computers and new hardware have automated some previously manual processes—in particular, control of speed and routing of freely rolling railcars in hump yards—the fundamental process of sorting cars and associated facility designs have changed very little since hump yards were first invented nearly a century ago. In the single-stage sorting approach commonly in use today, each block is assigned its own track. Each car must be sorted only once, but the maximum number of blocks built is limited to the number of tracks available. For example, a 50track yard could build a maximum of 50 blocks at one time using a single stage approach. Yards designed for single stage sorting need a large number of tracks, so they can build the maximum number of blocks possible. Since cars are sorted into many tracks, individual tracks can be short. Usually there are not enough tracks to build all needed blocks, so small blocks typically have only part-time availability in the yard.
By contrast, multiple stage sorting needs fewer tracks, but each car must be sorted more than once. For example, using the “geometric” or “triangular” sorting patterns (see FIGS.
1
and
2
), four trains with a total of 29 or 26 blocks, respectively, can be built simultaneously using only four tracks. Yards designed for multiple stage sorting need only a few tracks, but since each track must hold several blocks at once, tracks should be long enough to hold an entire train. The requirement to process cars more than once also implies a need for a high capacity hump.
Multiple-stage sing is undeniably a more powerful approach, but in the United States the need to process cars more than once has been viewed as costly and inefficient, so it has not been commonly applied in practice. Indeed, facilities designed for single-stage sorting are not well suited for multi-stage sorting because of differences in the basic design parameters for each kind of yard. But as will be shown herein, in a properly designed facility multiple-stage sorting can be not only more powerful, but even more efficient than single stage sorting because the costly flat switching operation at the “trim” end of the yard can be eliminated altogether.
A primary objective of this invention is to provide railroads a practical means to classify cars on a priority basis. While some cars don't need to move on any particular schedule, other cars have strict delivery deadlines. Although it is always desirable to be able to increase train capacity to handle all traffic on a same-day basis, it is not always possible to increase capacity nor would it always be economical. So in the event an outbound train has more cars than it can carry, it is essential to make certain that any cars having no remaining slack time in their delivery commitments have first access to available train capacity.
But today, because of the severely limited capabilities of single stage sorting, cars are sorted by destination block only, and not by specific outbound train. The scheme is essentially first come first served rather than reflecting the priority of individual shipments. Some cars not needing to go may occupy space needed to accomodate higher priority shipments, resulting in unnecessary missed connections and service failures.
If airlines (like railroads) allowed passengers to board aircraft without regard to whether they held tickets for a flight, revenue management would be impossible. The implications for railroads should be clear: to take advantage of revenue management technology which has been successfully applied by many other industries—including railroads' direct competitor, the trucking industry—it is essential that classification yard performance be improved to the level where connections can be guaranteed to specific trains. Yet, even very recent published literature as in Gallagher, J. (1999) Reconsider This,
Traffic World
, Jul. 12, 1999 on pp. 32-33 still holds that “you can't use data in real time to modify the way you handle individual cars. It's impractical.”
Prior Art Methods of Single Stage Sorting
Traditionally, large hump yards are subdivided into three separate areas, with tracks dedicated to specific functions: (a) Inbound trains; arrive on the receiving tracks. Cars are inspected for mechanical defects and air brakes released so cars can roll free. (b) To classify an inbound train, a switch engine couples to the train in the receiving yard and then shoves cars to the hump, where they are uncoupled and individually roll into their proper classification tracks by gravity. (c) Once enough cars have been collected to run an outbound train, or the scheduled “close-out” time arrives, blocks of cars are pulled from the “trim” end of the yard (opposite the hump) by switch engines and moved into the departure trac
Kettlestrings Donald A.
Morano S. Joseph
Olson Lars A.
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