WO2002042142A1 - High capacity multiple-stage railway switching yard - Google Patents

Abstract

A high capacity, multiple-stage railway car switching yard connects together two or more subyards as shown in Figure 1. Each subyard has a fully open arrival/departure end (80) and may have a continously descending gradient throughout the entire length of its classifications tracks (55). The subyards are positioned opposite one another, so classification tracks of one subyard can serve as receiving tracks for another subyard. Escape tracks (10a, 10b) are interconnected between the two subyards to provide a higher capacity and more efficiency and flexibility than a single yard by itself.

Description

HIGH CAPACITY MULTIPLE-STAGE RAILWAY SWITCHING YARD

CROSS-REFERENCE TO RELATED APPLICATIONS

The corresponding United States application of this application (serial number 09/917,636, filed 31 My, 2001) is a continuation-in-part of United States application serial number 09/716,300, filed 21 November, 2000 for Priority Car Sorting In Railroad Classification Yards Using a Continuous Multi-Stage Method.

TECHNICAL FIELD

This invention relates to railroads, particularly to methods of sorting cars in railroad yards.

BACKGROUND ART

Copending utility patent application Priority Car Sorting In Railroad Classification Yards Using a Continuous Multi-Stage Method by Edwin R. Kraft, serial number 09/716,300 (hereinafter referred to as the "parent application") describes new methods of multiple stage sorting in railroad classification yards. It also suggests several new yard designs to maximize the effectiveness of those methods. An extensive review of prior art is also included in the parent application. Further refinements to those operating methods and yard designs are disclosed herein.

Copending United States application serial number 09/716,300 is incorporated by reference into this application, as provided by Manual of Patent Examining Procedure, Section 608.01(p). However, some repetition of material already covered in the parent application is necessary. In cases where drawing figures or tables from the parent application are referenced, they keep their same figure numbers (1-22), labels and reference numbers herein. Therefore, any repetitive material which does need to be included herein can easily be identified and cross referenced with the parent application. Prior art designs for large railway classification yards dedicate specific tracks to distinct functions of receiving inbound trains, classification (sorting) of cars, and to assembly of outbound trains. Cars always move in a predetermined sequence from the receiving yard through the classification yard, and finally into the departure yard. Hump yards are modeled after an assembly line. The problem is that it is a rigid Henry Ford, 1920's-style assembly line, rather than adapting yard design to current just-in-time manufacturing paradigms ~ which emphasize flexibility, short setup times and rapid response to changing and always unpredictable customer needs. This lack of flexibility inherent in current yard designs translates into an inability to:

(a) make connections as scheduled,

(b) protect capacity on outbound trains needed for higher priority cars, (c) accommodate "block swapping" or

(d) benefit from switching already done at a previous yard. Accordingly, major changes in design philosophy are needed to make hump yards effective in today's truck-competitive environment. Currently, hump yards generally use single stage sorting, where each car is classified only once. Single stage sorting is very restrictive, since it limits the number of classifications or "blocks" that can be built to no more than the number of tracks in the yard, and once cars are classified, affords no "second chance" to adjust the arrangement of cars. Even if a yard is built with many short tracks, single stage yards often cannot create as many blocks as are needed. Since classification tracks are usually too short to assemble outbound trains, cars have to be pulled out of the opposite end of the yard, called the "trim" end and moved into a separate departure yard having longer tracks. Usually this "flat" switching operation, and not the sorting capacity of the hump, limits maximum throughput of the yard.

In a multiple stage yard, each car may be classified more than once allowing cars to be sorted into many more blocks (distinct classifications) than the number of tracks available. As shown in the parent application if classification tracks are of sufficient length, trains of more than one block can be built "ready to go" on a single track in proper order for departure, without needing flat switching at the trim end of the yard. The second sorting stage at the hump replaces flat switching for outbound train assembly, resulting in no net increase in switching workload. Having eliminated the flat switching bottleneck at the "trim" end of the yard, the capacity of a multiple stage yard is clearly constrained by the hump processing rate. A high processing rate is needed since each car must be classified two or three times in a multiple stage yard, as compared to only once in a single stage yard. This need for high capacity has been recognized for a long time, in fact, a lack of sufficient capacity using traditional gravity sorting has been thought to render multiple stage switching infeasible. In The Folded Two Stage Railway Classification Yard, (hereinafter referred to as Davis, 1967) on p. 55 the two-fold yard was characterized as "a new concept in yard design. It may never have been proposed before because it would be inoperative using the sorting techniques presently employed by railroads. The yard uses neither an engine nor gravity to separate the cars." Instead, Davis proposed use of a mechanical car accelerator to boost sorting capacity. Although some U.S. yards have classified over 3,000 cars per day across a single gravity hump, with the increasing weight and length of modern cars, yard capacity has been slowly reduced. A typical hump yard today classifies 2,000- 2,500 cars per day. A multiple stage yard of the same capacity would need a humping capability of 5,000- 7,500 cars per day. This invention shows how the capacity needed to enable practical multiple stage sorting can be attained within the proven capabihty of conventional gravity switching, without needing to resort to any exotic or untested mechanical devices for accelerating or controlling the speed of railcars.

Shortcomings of Previous Designs

Figure 10 of the parent application shows a design for a multiple stage classification yard. This yard consists of a single body of long classification tracks 55, which should have a 75 slight descending gradient throughout their entire length, so cars will roll all the way to the ends of the tracks. With such a gradient, car speed can be adequately controlled using only retarder units, avoiding the necessity for more expensive booster units. Figure 22 of the parent application shows how "Dowty" car retarders may be distributed throughout the entire length of each track to maintain continuous speed control of cars, and to stop the cars upon reaching the

80 end of each track.

The design of Figure 10 of the parent application permits maximum flexibility in use of classification tracks for receiving inbound trains, sorting of cars and for final assembly of outbound trains. Cart roads 60 between every pair of tracks allow convenient access by mechanical personnel for performing car inspection and repairs, and for ma taining tracks,

85 switches and car retarder systems.

Means for accelerating cars 90 into the classification tracks (generally assumed to be a gravity hump) are provided at one end of the yard. Switches at the opposite end of the yard, called the arrival/departure end 80, allow trains to arrive and depart the yard onto the mainline 30 without interfering with hump 90 activities. Flat switching can also be performed at the

90 arrival/departure end 80, permitting "swapping" blocks of preclassified cars directly from one train to another, avoiding the need for those cars to be processed over the hump.

The main weakness of the yard shown in Figure 10 of the parent application is that it only allows one train to be processed at a time. This severely constrains its capacity. Figures 14 and 15, also from the parent application, suggest placing a hump on both ends of the yard to 95 increase its sorting capacity. However, such "double ended" designs can be problematical for the following reasons:

(a) It becomes necessary to coordinate processing activities of two humps at both ends of the yard, since cars cannot be safely humped into a track from both directions simultaneously.

(b) Double ended designs cause difficulties in establishing proper gradients throughout the 00 length of the yard. Cars would tend to collect at the low point of the yard in the middle, rather than rolling all the way to the ends of the tracks. This problem could be overcome, at some cost, by employing booster units (an optional feature of the "Dowty" retarder system) to keep the cars rolling.

(c) Humps 90a and 90b on both ends of the yard block access to classification tracks 55 05 needed by arriving and departing trains, and also prevent flat switching. Although the lapped design as in Figure 15 of the parent application partially addresses the problem, a fully open arrival departure end 80 as shown in Figure 10 of the parent application is even more desirable to minimize interference with hump 90 operations.

(d) Finally, sorting activity in a double-ended yard may become so intense as to render 10 impractical the inspection and repair of cars while they Me in the classification tracks. This defeats one of the main benefits of multiple stage switching, which is the abiMty to effectively utiMze car time waiting for connections to perform maintenance and other mechanical servicing activities. DISCLOSURE OF THE INVENTION The high capacity multiple-stage yard of Figure 1 , which consists of two subyards, does not suffer the limitations associated with a double ended design. Each subyard has a fully open arrival/departure end, and may have a continuously descending gradient throughout the entire length of its classification tracks. The design of Figure 10 in the parent application which is used as a template, can be repMcated as many times as needed to attain the needed total capacity. The key to success of this design is positioning the subyards opposite one another, so classification tracks of one subyard can serve as receiving tracks for the other subyard. By interconnecting the escape tracks 10 between the two yards as shown in Figure 1, the faciMty not only has higher capacity but even more efficiency and flexibility than a single yard by itself.

A very simple, but critical improvement shown in both Figures 1 and 3 is provision of a double hump lead track 40. By providing scizzors crossovers 140 at the hump crest, any classification track 55 can be reached from either hump lead track 40. (These are labeled 40a, 40b, 55a, 55b, 140a and 140b in Figure 1 because those features are replicated in both subyards.) Although double hump leads with crossovers are often provided in single stage yards, they are of limited value since parallel hump operations frequently interfere with one another. In a single stage yard a second hump lead can be used to preposition trains for processing, but seldom can two humping operations proceed at once. But in a multiple stage yard during second stage sorting, cars are sorted into just a few tracks representing the outbound train(s) currently being assembled. If all these tracks are located on the same side of the yard, two hump operations can proceed concurrently without interference. Since over half the hump processing time in a multiple stage yard is consumed by second stage sorting, dual hump leads can be of considerable value. In a multiple stage yard, dual leads are much more useful than in traditional single stage yards, since they can boost capacity by at least 50%.

By providing two subyards as shown in Figure 1, capacity is further doubled, since operations in the two subyards do not interfere with one another. By providing four hump switching leads (as compared to only a single lead in the yard of Figure 10 in the parent application) hump capacity is increased by a factor of at least three times. By comparison, using the triangular sorting pattern, each car must be sorted on the average between 2.5 and 3 times. Therefore, it should be apparent that the capacity of the yard of Figure 1 will be comparable to that of a large conventional single stage yard. This is accomplished without requiring inordinately high hump processing rates or any unusual mechanical means for accelerating or regulating the speed of cars. This capacity is achievable using conventional, proven gravity switching methods, and assumes that each car will have to be classified up to three times before it finally departs the yard. 150 The preceding discussion shows how the required capacity increase can be achieved through physical design of the yard facilit . However, capacity can be further increased and costs reduced even more by utilizing the special yard operating methods proposed here. The first method exploits specific features of the track configuration shown in Figure 1. The second method reUes on a system of partial preclassification of cars to eliminate the need for first stage

155 sorting, which by itself can almost double yard capacity. That method can be utilized in the yard of Figure 10 in the parent apphcation as well. Each of these operating methods are detailed in the following sections.

Objects and Advantages

Several objects and advantages of the present invention are:

160 (a) As shown in Figure 3, capacity can be increased by providing a double hump lead with scizzors crossovers instead of only a single switching lead across the hump. Using this second hump lead during second stage switching operations can boost capacity by at least 50%.

(b) By positioning two or more subyards opposite one another, interconnecting the escape tracks and providing crossover tracks in the classification yard as in Figure 1, one subyard can

165 receive trains for processing in the opposite subyard. This eliminates the need for one "pull back" move. With two subyards, operation as a "folded" yard also becomes possible. Provision of a second subyard (where each subyard has a double hump lead with scizzors crossovers) increases capacity by at least three times, as compared to the yard shown in Figure 10 of the parent application.

170 (c) Cars can be partially preblocked at preceding yards to bypass the first stage sort. By enabling better utilization of the double hump lead as well as directly reducing the number of cars that have to be switched, partial preblocking can more than double the capacity of the yard. Implementing all three improvements at once, the capacity of the yard of Figure 10 in the parent apphcation can be increased by a factor of at least six times.

175 Still further objects and advantages will become apparent from consideration of the ensuing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, closely related elements have the same number but different alphabetic suffixes. 180 Figure 1 shows a high capacity multiple stage switching yard having two subyards, with a total of four available switching leads;

Figure 2 shows a system of three yards — two satellite yards and a hub yard — where the satellite yards perform first stage switching for the hub; and

Figure 3 shows the yard of Figure 10 in the parent apphcation, with addition of dual 185 switching leads with scizzors crossovers across the hump. BEST MODES FOR CARRYING OUT INVENTION AND INDUSTRIAL

APPLICABILITY

Reference Numerals In Drawings

10 Hump Escape Track 100 Eastbound Receiving/ Westbound Departure

20 Locomotive Servicing FaciMty Switches

25 Rurming Track 105 Middle Tracks

30 Main Line Track. 110 Westbound Receiving/ Eastbound Departure

35 Wye Track Switches

40 Hump Lead Track 115 Sorting Switches

55 Classification Tracks with Retarders 120 Dowty retarder units

60 Cart Road between each track 125 Rails

80 Arrival/Departure end 140 Scizzors Crossovers

90 Hump 150 Crossovers between Classification Tracks

Figure 1 — Preferred Embodiment

The preferred embodiment for a railway classification yard consists of at least two subyards "a" and "b", as shown in Figure 1, where each subyard is patterned after the yard of Figure 10 in the parent application. Subyard "a" consists of a double lead track 40a, means for accelerating cars 90a (normally a gravity hump) connected by switches 115a to classification tracks with cart paths 55a. These classification tracks 55a are in turn connected to the mainline 30 by another set of switches, which comprise the arrival/departure end 80a. Subyard "b" consists of a second complete set of identical elements 40b, 90b, 115b, 55b and 80b oriented in the opposite direction, and positioned so the escape tracks 10 of the two yards are interconnected. The escape tracks 10 serve three main purposes: (a) Escape tracks permit locomotives on arriving trains to move directly to the locomotive servicing faciMty 20, without interfering with sorting activities on either of the hump lead tracks 40.

(b) When a switching locomotive enters the classification tracks 55 to retrieve a cut of cars 225 for second stage sorting, cars can be puUed back to the hump lead tracks 40 via escape tracks 10 bypassing the hump. These escape tracks provide a relatively straight and level route out of the classification tracks 55, enabling the pull back operation to be performed faster, with less interference to hump 90 activities, and causing less wear on retarder systems and switches 115 in the yard. 230 (c) Escape tracks also offer an alternative to using arrival/departure ends 80 for mainline trains arriving or departing the yard. However as discussed in the parent apphcation, this use is undesirable, since it blocks access from the hump 90 to some outside classification tracks 55.

Each subyard may operate independently as a yard of Figure 10, as described in the parent application. However by coordinating activities between two subyards, some operations 235 can be performed that are not possible in a yard consisting of only a single body of tracks.

Receiving Trains in the Opposite Subyard

With provision of four humps in the high capacity yard, the bottleneck is no longer humping capacity, but rather the abiMty to continually feed cars to the humps as fast as they can be processed. The most time-consuming operation is the puU-back movement where a switch

240 engine enters the classification tracks to retrieve its next cut of cars. If those cars are pulled back via escape tracks 10 then access from the hump to some outside yard tracks is blocked. If cars are pulled back via the hump, the hump is completely blocked. If the humps can be fed without having to puU cars back from classification tracks, capacity is increased since interference with hump operations is reduced, and cars can be fed on almost a continuous basis.

245 In the high capacity yard of Figure 1 , the need for pulling cars back can be reduced if arriving trains are received in the classification tracks of the opposite subyard. To do this, crossover tracks 150 are used to allow trains to be shoved from the classification tracks of one subyard directly to the hump of the other subyard. For example arriving trains may be received in classification tracks 55a of subyard a, and shoved through the crossovers 150b directly to

250 hump 90b of subyard b. Only those classification tracks 55 having crossover tracks are accessible for this purpose. Rather than building a separate receiving yard, with the design of Figure 1 classification tracks 55 can be flexibly used as receiving tracks when such receiving tracks are needed; and reused for classification or departure purposes at other times.

Another method for reducing puU-backs is operation as a two-stage folded yard. If cars

255 in the first sorting stage are coUected in the classification tracks 55 with crossovers 150, they can be humped directly back into the opposite subyard without having to pull them back. The two-stage folded yard, studied extensively by Davis (1967), is best suited for arithmetic rather than triangular sorting. The differences between those two sorting methods are fuUy described in the parent 260 application. However, the main benefit of arithmetic sorting (also called the "Sorting by block" method) is that it needs only two classifications per car, compared to triangular sorting which requires up to three classifications per car.

The major disadvantage of arithmetic sorting is that aU needed yard tracks must first be cleared of other cars, and dedicated exclusively to this operation for an extended period of time. 265 Track space needed to support arithmetic sorting may not always be readily available, which

Mmits the potential appMcabiMty of this method. Still, use of arithmetic sorting instead of triangular sorting can reduce the number of cars needing to be switched, whenever circumstances permit its application.

Partial Preblocking of Cars to Bypass the First Stage Sort

270 Most current hump yards cannot benefit from preclassification work already done for them. This stems from inflexibility of their track design, and from limitations of their radar systems used to control conventional "clasp" car retarders. Reflecting the inflexible "assembly line" design philosophy used in most yards, no convenient way to move a preblocked group of cars directly from the receiving yard to the departure yard is provided. A special switch engine

275 move is usually not considered worth the effort.

Cars humped in multiple do not accelerate the same as individual cars, so the radar system used to control the retarders has difficulty determining the force needed to adequately control car speed. Because of this limitation most yards cut off only one or a few cars at a time, even if all the cars are destined for the same track. Usually hump yards find it faster to process

280 cars individually rather than flat switching across the hump.

The multiple stage yards of the parent application and of Figures 1 and 3 of this application do not suffer either of those limitations of prior art single stage yards. First, since classification, arrival and departure functions are all combined into the same set of tracks, it is easy to flat switch preclassified blocks of cars at the arrival/ departure end, elirninating the need

285 for those cars to pass over the hump. Second, since the yard utiMzes distributed (e.g. "Dowty") retarders instead of radar-controlled clasp retarders, cars can be humped in multiple without difficulty.

M. A. Schlenker, in his 1995 MIT Master's thesis Improving Railroad Performance Using Advanced Service Design Techniques: Analyzing the Operating Plan at CSX

290 Transportation (hereinafter referred to as Schlenker, 1995) on pp. 83-110 proposed a new concept, caUed "Tandem Humping" in which the two stages of arithmetic sorting would be performed in separate hump yards. While the method of partial preclassification disclosed herein may resemble tandem humping, there are also a number of important differences as shown in Table 1. By taking advantage of yard faciMties specificaUy designed to support the needed

295 switching operations, partial preclassification avoids many Mmitations of tandem humping, and offers a number of improvements over that prior art method.

Table 1 - Comparison of Tandem Humping to Partial Preclassification Traditional methods of preclassification, caUed "block swapping" call for a preceding

300 yard to build a block which would normaUy only be built at the central hub yard. When such preclassified cars arrive, they can be flat switched directly onto an outbound departing train. Block swapping allows bypassing both the first and second sorting stage. However, with multiple stage sorting, a new kind of preblocking opportunity presents itself: cars can be partiaUy preblocked to bypass only the first sorting stage. This approach to yard operations is novel since

305 it practicaUy reverses the traditional direction of flow of cars through the yard. To see how it works, consider a system of three yards as shown in Figure 2 - two (or more) sateUite yards; and a central hub yard which resorts all cars received, whether partiaUy preclassified or not, for points beyond.

The hub yard must publish its plan for intermixing blocks on the same track in the first

310 stage sort. Knowing ahead of time which blocks are combined, satellite yards can preclassify their cars to bypass the first stage sort at the hub. Cars need not be separated among blocks that are to be combined on the same track, so preblocking is based upon the track assignment at the hub yard. Trains prearranged in this manner can be flat switched upon arrival at the arrival/departure end. The cars end up in exactly the same placement in the classification tracks as

315 if those trains had been humped. The whole train does not need to be preblocked — if only two or three tracks with the most cars were preclassified, it would still offer a considerable savings over having to process the entire train at the hump.

Figure 2 shows how partial preblocking can be used in conjunction with the triangular sorting pattern. The hub yard builds an outbound train of six distinct blocks, one thru six, in

320 that sequence. As in the figures of the parent apphcation, parentheses in Figure 2 indicate intermixed groups of cars. Thus it can be seen that the outbound train consists of six distinct blocks in the proper order, and the cars are not intermixed between blocks.

Of course, those cars arriving at a yard are the same cars which eventuaUy depart; the sateUite yards see that blocks numbered 1,3 and 5 are intermixed on the same track at the hub

325 yard; blocks 2 and 6 are intermixed on another track, while block 4 is on a track by itself (or possibly intermixed with cars for another train, not shown.)

Therefore each sateUite yard b lds a train of three blocks; mtermixing cars for hub blocks 1,3 and 5; then 2 and 6; finally block 4 by itself. These two trains each arrive at the hub yard and are flat switched into the classification tracks from the arrival/departure end.

330 Once both trains have arrived and placed their cars, as described in the parent application a switch engine enters the classification tracks 55 (Figures 1 or 3) and pulls back the track containing the blocks 1,3 and 5 for hump processing. After the remaining two tracks have also been processed, the outbound train is complete on a single track ready for departure.

Note that this sequence is practicaUy the opposite of what is practiced in conventional

335 hump yards today. Conventional yards use the hump to process newly-arriving trains, but they rely on flat switching for train assembly. The process of partial preblocking reverses this. Newly arriving trains are flat switched into the classification tracks wbrile the hump is used for final train assembly. The advantage of this process is that it becomes very easy to separate any unwanted, low priority cars in excess of train capacity at that hump just prior to departure. The

340 significant benefit of being able to utilize otherwise-idle car time awaiting connections to perform mechanical inspection and repair is also preserved.

Partial preblocking can be justified in many cases where traffic volume would be insufficient to support a conventional bypass block. A practical rule of thumb is that a bypass block must have at least fifteen cars per day to be justified. To justify a block swap, each

345 individual block must satisfy this minimum requirement of fifteen cars per day. But for partial preblocking, the decision is based on the combined volume of aU blocks grouped together on the same track, not on volume of any individual block.

By reducing the proportion of hump time spent in first stage sorting, partial preblocking increases the productivity of the double hump leads. These double hump leads are reaUy only

350 useful during secondary sorting operations. During first stage sorting, only one train at a time can be humped since cars may be randomly sent to almost every track in the yard. But during secondary sorting, since cars are sent only into a Mmited number of tracks, both hump leads can work concurrently. This has a multiplier effect on capacity — for every car preblocked, capacity of the multiple stage yard is increased by an even greater amount. Effective use of partial

355 preblocking can more than double the capacity of a multiple stage yard.

Use of partial preblocking does not limit the abihty of the hub yard to assign blocks to tracks in any way desired ~ for example, the continuous sorting pattern proposed in the parent application can stiU be used. The steps required to implement a pattern of continuous sorting as disclosed in the parent apphcation are unchanged, except for the added caveat that the first

360 sorting stage may now be performed in a preceding yard.

Partial preblocking also does not interfere with removal of lower priority cars in excess of train capacity, since the second stage sort is stiU performed. In this respect, partial preblocking is superior even to block swapping, which affords no opportunity to adjust the consist of the cars being swapped or to remove low priority cars from that block. The steps required to

365 implement a priority-based sorting process as disclosed in the parent apphcation are unchanged, except for the added caveat that the first sorting stage may now be performed in a preceding yard.

FinaUy, partial preblocking actuaUy enhances the abihty to inspect and repair cars while they lie in the classification tracks. Secondary sorting operations don't interfere with mechanical

370 operations on tracks that are not receiving cars, so interruption to mechanical operations is limited to the length of time needed to flat-switch cars into each classification track. By decreasing the amount of first-stage sorting needed at the hump, the method of partial preblocking maximizes productivity of mechanical personnel in the yard by keeping interruptions to a minimum. 375 Figure 3 « Alternative Embodiment

An alternative embodiment consists of the yard of Figure 3, operated by the method of partial preblocking of cars to bypass the first stage sort. In Figure 3, a double hump lead with scizzors crossovers 140 has been added to the yard of Figure 10 in the parent apphcation, to allow paraUel humping to proceed concurrently during the second stage sort. If adequate

380 preblocking support can be provided, the yard of Figure 3 could handle as much traffic as a large conventional single-stage yard, without needing the second sub-yard as shown in Figure 1.

The best yard design for any given locale depends on the number of cars needing to be switched, land availability and cost, and the degree to which surrounding yards are able to provide preblocking support. However as a rule, the simplest design capable of providing the

385 required capacity should be chosen. The more compMcated design of Figure 1 should be introduced only when the simpler yard of Figure 3 is unable to handle the anticipated traffic volume.

Accordingly, a variety of means exist to increase capacity and boost efficiency of multiple stage classification yards. These include both physical improvements to the track design, as well

390 as improved operating methods. In approximate order of priority, the foUowing steps can be taken to increase the capacity of multiple stage switching yards:

(a) Provide a second hump switching lead, to aUow parallel humping operations to proceed concurrently during second stage sorting. A second switching lead should always be provided as a standard feature of any multiple stage switching yard.

395 (b) PartiaUy preblock cars at preceding yards so the first sorting stage can be bypassed.

Those cars can be flat switched at the arrival/departure end instead of having to be humped. Not only does this result in a direct reduction in the number of cars needing to be processed but actually increases the sorting capacity of the yard, since a higher proportion of the hump time is spent in second stage sorting where the dual hump leads can both be used.

400 (c) Provide a second subyard as shown in Figure 1. In addition to doubhng the number of hump switching leads, cars can be shoved directly to the hump of the opposite subyard eliminating the need for one puUback move. The second subyard also provides a limited capability to operate as a two stage folded yard.

This apphcation shows that multiple stage switching on a large scale is feasible with 405 conventional hump processing. Within the proven capabilities of conventional gravity switching, such yards can be configured to offer sorting capacity comparable to the largest of today's single stage yards. Although the description above contains many specificities, these should not be construed as limiting the scope of the invention, but as merely providing iUustrations of some of the presently preferred embodiments of the invention. Thus the scope of the invention should be 410 determined by the appended claims and their legal equivalents, rather than by the examples given.

Claims

1. A method of increasing the raUway car handling capacity of multiple stage railway switching 415 facihties by partiaUy preblocking railway cars at more than one preceding yard to bypass a first stage sort at a central hub yard, comprising the steps of:

(a) determining which blocks wUl be intermixed on the same tracks at the central hub yard in the first stage sort,

(b) pubMshing a plan for termixing said blocks on said tracks, so said predecessor yards may 420 be aware of which groups of cars are combined versus kept separate at the hub yard, and

(c) at each said predecessor yard, separating cars into distinct groups based on the track assignment they wUl receive at the hub yard, whereby said distinct groups of cars are arranged into trains, so those cars can be flat switched upon arrival directly into classification tracks at the hub yard, without needing to be classified at 425 the hub yard by individual car in said first stage sort.

2. A method of sorting a plurality of railcars into a plurality of outbound trains on a plurality of tracks, comprising the steps of:

(a) initially arranging said raUcars on a plurality of said tracks in a predetermined mathematical sorting pattern such that said raUcars of more than one train or block may be

430 intermixed on any single said track in a first stage sort,

(b) offsetting and overlapping the mathematical sorting pattern of track assignments of said railcars for different trains or blocks in said first stage sort, for enabling the sorting process to be sustained on a continuous basis,

(c) coUecting said railcars on said tracks for an interval of time until the first outbound train 435 must be readied for departure,

(d) retrieving said railcars from said tracks in a predetermined sequence, and

(e) rearranging said railcars on said tracks one or more additional times as required by the predetermined mathematical sorting pattern, such that said railcars are no longer mtermixed but are separated into distinct trains which may have more than one block on a single track,

440 whereby said raUcars wUl be arranged into trains ordered in a proper block sequence for departure and the sorting process can be sustained on a continuous basis; and wherein said first stage sort may be performed at a preceding yard, so said raUcars can be flat switched into classification tracks without having to be individually sorted.

3. A method of predetermining connections of specific railcars to specific outbound trains, 445 comprising the steps of:

(a) initially arranging said raUcars on a pluraUty of said tracks in a predetermined mathematical sorting pattern such that said raUcars of more than one train or block may be intermixed on any single said track in a first stage sort,

(b) collecting said raUcars on said tracks for an interval of time untU the first outbound train 450 must be readied for departure,

(c) retrieving said raUcars from said tracks in a predetermined sequence, and

(d) rearranging said railcars on said tracks one or more additional times as required by the predetermined mathematical sorting pattern, such that said raUcars are no longer mtermixed but are separated into distinct trains which may have more than one block on a single track,

455 (e) removing from the train any of said raUcars in excess of train capacity, or which are undesired by the customer during a second stage, third stage or later sort, whereby only preselected of said raUcars are included in the train, and aU other of said railcars are separated to remain in the yard or depart on a different train; and wherein said first stage sort may be performed at a preceding yard, so said raUcars can be flat switched into

460 classification tracks without having to be individuaUy sorted.

4. A method of performing inspection and repairs of raUcars, utilizing otherwise idle time of railcars while said raUcars are awaiting outbound connections on tracks, comprising the steps of:

(a) initiaUy arranging said raUcars on a plurality of said tracks in a predetermined

465 mathematical sorting pattern such that said raUcars of more than one train or block may be intermixed on any single said track in a first stage sort,

(b) collecting said raUcars on said tracks for an interval of time until the first outbound train must be readied for departure,

(c) retrieving said railcars from said tracks in a predetermined sequence, and

470 (d) rearranging said railcars on said tracks one or more additional times as required by the predetermined mathematical sorting pattern, such that said raUcars are no longer intermixed but are separated into distinct trains which may have more than one block on a single track,

(e) during a second or later stage sorting operation, inspecting and repairing said raUcars on tracks which are not receiving any other raUcars during said second or later stage sorting

475 phase; whereby inspection and repairs of said raUcars may be safely performed whUe the raUcars he on classification tracks; and wherein said first stage sort may be performed at any preceding yard, so said raUcars can be flat switched into the classification tracks without having to be individually sorted.

480 5. A raUcar sorting faciMty connected to a mainline, branch or secondary track, comprising two or more subyards, each subyard comprising: a plurality of classification tracks onto which railcars can be sorted and stored until departure from said sorting facUity, the lengths of each said classification tracks being substantiaUy equal to a normal train length typicaUy operated in the geographic territory in which 485 said sorting faciMty is located; at least one switching lead track and means for accelerating individual raUcars or groups of railcars connected in operative relationship with each other and with said classification tracks for enabling acceleration of individual raUcars, or groups of raUcars onto said classification tracks whUe providing adequate separation between groups of raUcars to aUow for safe sorting

490 operations; a first plurality of track switches connected in operative relationship with said switching lead track or tracks and said classification tracks for routing said railcars, or groups of raUcars, onto said classification tracks and for selecting which of said classification tracks wiU receive each of said railcars or group of railcars;

495 means in operative relationship with said classification tracks for decelerating said railcars, or groups of raUcars, and for controlMng their coupling speed within safe limits; means in operative relationship with said classification tracks and with said mainline track for enabMng arrival and departure of inbound and outbound trains directly from said classification tracks, and for enabling arriving trains to be received onto said classification tracks

500 for storage while awaiting processing, whereby through apphcation of multiple stage switching methods, trains of more than one block may be ordered in proper standing order sequence ready for departure on a single said classification track, eliminating the need for raUcars to be switched into a separate set of departure tracks for final train assembly; and additional tracks connecting said subyards to aUow trains received in designated tracks of

505 one subyard to be processed in another subyard.