Railroad Classification Yard
Guylee Washington
Coastal Pines College
February 25, 2015

Railroad Classification Yard
Do you know what a railroad classification yard consist of? In railroad freight transportation, shipments are consolidated to benefit from economies of scale. Railroad classification yards, also called shunting yards, play an important role as consolidation nodes in rail freight networks. At classification yards, inbound trains are disassembled and the railcars are sorted blocks. Through this procedure, railcars can be routed through the network in a series of blocks moving on trains in such a way that every destination pair can be served while avoiding a large number of end-to-end connections. Due to the complexity of terminal operations, computer simulation offers a flexible and credible technique to identify more opportunities for yard performance improvements. However, the use of simulation technique to model terminal operations is not a common practice in freight railroads. Throughout this report I will be explaining key factors that depicts the typical operations in a railroad hump yard and performance measurements that are used to gauge the efficiency of yard operations.
In North America, railroad classification yards are classified into two main types: hump yards and flat yards. Did you know that “More than half of the hump yards in North America have closed in the past 25 years? From 152 operating classification yards in 1975, the number dropped to 122 in 1985, and 72 by 1993. In 2002, there were 59 active hump yards” (North America). Mergers and consolidations, and the shift in traffic from boxcars to containers, were the reason for the major decline in North America. A typical north America hump yard is generally divided into three main areas, each of which consists of a set of parallel tracks: the receiving yard, where inbound trains arrive and are prepared for sorting, the class yard or bowl, where railcars are sorted into blocks and the departure yard, where blocks are assembled into outbound trains, inspected and then depart.
“The majority of space in any yard is devoted to the classification of trains”. (Railroad yards) When planning a yard, having more tracks doesn’t mean that particular location has the better yard. The most efficient yard is displayed by how the tracks are arranged. This is true because, if a yard is known for having freights backed up all the time then, many engineers wouldn’t recommend entering that specific yard in future transports.
There are four different tracks that make up an efficient classification yard. Each track is limited with a track capacity constraint in terms of the maximum number of railcars that each track can hold in the corresponding area. The track capacity is limited to a specific number of railcars, for the receiving area, classification area and departing area. There is always room for improvement in every yard, but in most yards there is single dedicated track, located off the mainline, that helps better operations. Any incoming train that comes into a yard will be switched from the mainline to this particular track. “As you can see, this allows operations to take place without stopping action on your main loops, or active switching in the yard itself”. (Railroad Yards) In a hump yard, the sorting is accomplished by moving the inbound trains to the top of a specially-designed and uncoupling the cars one-by-one or in small cuts. A cut is any set of cars moving together from one place to another in the yard. Then gravity takes over and the cars roll into the classification tracks with their speed regulated by rail-mounted brakes called retarders. The railcars then wait in the classification yard until it is time to assemble the blocks into outbound trains. Blocks are a set of cars that has been grouped together in a departing train because they share the same station destination. The blocks are moved to the departure yard thru a system of tracks and switches with most trains consisting of one or more blocks.
The classification area is often connected to the receiving area by one or more hump lead tracks; these leads allows for a repeated classification of railcars. The car storage capacities of these areas are mainly determined by the number of available tracks and their length. Due to limited space and scarcity of other resources, yards are physically capacitated in terms of the number of cars that can be classified, the number of blocks that can be made in a given time period, the number of trains that can be received in a given time period, and the number of trains that can be dispatched in a given time period.
The primary interest in a yard is a railcar. Each railcar will move through these main terminals such as the train arrival, inbound inspection, classification, and building of outbound train, outbound inspections, and train departure.
During the inspection area trains that enter the receiving area and are prepared for inspection release the air pressure of the braking system so that the railcars can roll freely over the hump. Since only one cut of railcars can be sorted at a time, the receiving area needs to make sure there is enough storage space for the trains that arrive later. When a train is ready for classification, it is shoved out of the receiving area. Each railcar of an inbound train is made to run into the classification track to which it is assigned. Typically, the classification tracks in the classification area are already occupied by existing freights. Ideally, the humped railcars will roll all the way to the existing railcars and will attach to them automatically. Due to a variety of factors, enough time is needed to be allocated for the cars to be coupled together by either the hump engine or by one of the pull-out engines as part of the build train process. “This is the heart of the yard, where trains are sorted by destination into new blocks. These blocks can then be combined in the departure yard to form new trains” (Kunkle).
During the outbound area trains leave the yard from the departure area. Engines pull blocks of railcars from the departure end of the classification tracks and shove them to their designated tracks in the departure area. The blocks are assembled in accordance with the order of the train’s destination station to make up the outbound trains. Once all of the blocks for a particular train are assembled, the train is inspected for any problems on all of the cars are connected. A train waits for its permission to enter the mainline to start its departure.
In conclusion, this paper gives and overview of the operation of a hump yard. Hopefully readers will be able to understand all the task that are performed during each terminal in a classification yard.

References
Kunkle, R. (n.d.). Classification Yards - Planning Classification Yards for Model Railroads. Retrieved February 12, 2015, from http://modeltrains.about.com/od/layoutconstruction/a/ClassYardPlanning.htm
North America's hump yards. (2006, July 8). Retrieved February 12, 2015, from http://trn.trains.com/railroads/2006/07/north-americas-hump-yards
Railroad Yards - Adding a Classification Yard to Your Layout. (2012, May 09). Retrieved February 12, 2015, from https://lionelllc.wordpress.com/2012/05/09/railroad-yards-adding-a-classification-yard-to-your-layout/