Railroad Operations – The Interchange

18 04 2012

Look at a typical freight train anywhere in North America today and you’re bound to find cars from every corner of the continent. So, how did that Burlington Northern boxcar show up in New York? If “Southern Serves the South,” why can you find their boxcars on trains in Minnesota? The answer is the interchange.

Simple Interchange

This simple interchange would be perfect for a small model railroad. Once a connecting track between a Reading branch line and the Pennsylvania's mainline at Salunga, PA, today this marks the connection between the Landisville Railroad and Amtrak (Norfolk Southern.) The curved track with the boxcars is the old connection. The PRR mainline can be seen under catenary in the background. These two cars are spotted for a local lumber yard. Three more cars for interchange with NS are hidden just behind the stacks of lumber. A simple siding like this gives you two industries in one!

Simply put, an interchange is a point at which two different rail lines meet and can exchange cars. Sometimes entire trains change hands, sometimes there is a siding where individual cars can be picked up or set off to make the connection. The practice of interchanging cars means once a shipper loads a car, that load won’t be touched again until it arrives at its destination. It also allows railroads to cooperate and serve customers to which they could never afford to extend their tracks. For trackside observers, interchange makes every train an opportunity to see something new. For modelers, it gives license to add bits of all your favorite railroads to your layout with complete authenticity.There is more to the interchange than just handing over a car however. For an interchange to work, all of the cars exchanged must meet the same set of standards. From the gauge of the wheels to the height of the couplers, to the maximum weight and height, to the size of standard parts like journals and brakes, to the lettering on the sides of the cars – if standards aren’t established and met, cars may not fit on another railroad, attach to other equipment, be repaired offline if something goes wrong, or even be understood and routed by other employees. The first summit to create standards for interchange in the United States was reached this week in 1866 (April 20 to be exact.) But there were agreements between railroads and limited exchange of cars prior this, especially in the northeastern part of the United States.

Apache Interchange

An interchange can be a colorful spot. Here at Holbrook, Arizona, Apache RR Alco's can be seen next to modern BNSF GE's and EMD's on their busy ex-Santa Fe mainline. If you can't decide on a favorite railroad - pick a place where you can model more than one!

As the rail network grew following the Civil War, increased standardization and cooperation would be necessary. But all of this free-exchange of cars wasn’t really free. If a customer’s shipment needed to travel over multiple rail lines to reach its destination, each company wanted its share of the rate. But no customer wanted to put up with the hassle of booking their shipment on two, three or even more railroads. And rabid competition between companies often led to widely varying rates between railroads and even between different destinations and for different commodities on the same railroad.

While the railroads themselves, through organizations like the Master Car Builders Association, established many of the physical standards for interchange (maximum car weights, standard journal sizes, common data decoration, etc.), the Interstate Commerce Commission became the ultimate arbiter of shipping rates. Standard rates for varying commodities, assigned based on mileage, were established to simplify things. (Although they still weren’t all that simple.) Customers would pay one railroad company (usually the one that delivered the car) and railroad billing departments would take care of the rest. Each carrier that had a hand in moving the car would be paid their fair share.


The big railroads interchange too. Here at Barstow, California, mainlines from Los Angeles and northern California converge from the west, and BNSF and Union Pacific mainlines split to the east. Once the site of a bustling passenger operation, a large freight yard still remains at this critical crossroads. The station and museum here are a great place to safely observe railroad operations in person. (The sunsets aren't too shabby either!)

There were also rates and regulations for empty cars to prevent a railroad from hoarding cars from other roads or routing competitors cars to less-friendly connections. Multiply these many rates and rules by the number of shippers by the tens of thousands of cars rolling along the rails at any given point and you can see why railroads had to employ thousands of workers whose daily processing of train movements never took them anywhere near the tracks.

The ability with which railroads accurately tracked all of these cars and their charges in days long before a computer was imagined is astounding and bewildering. But from a modelers’ perspective, we’re fortunate enough to just enjoy the fruits of all that labor. Simply by having a mixed consist of freight, you imply an active interchange on your line. But if you like operations, modeling an interchange is an easy addition to any layout.

Since an interchange is just a track which connects your railroad to another, adding one to your layout could be as simple as adding a siding. You could go further and have the connecting line disappear into a tunnel or simply end at the edge of the platform (just add a block to keep cars from going too far!) to imply the tracks continue to go somewhere. You could also build a more functional junction between separate tracks and exchange trains between two different lines. Setting off or picking up cars at the interchange is a great way to add a little operations to your layout, and unlike other industries that typically only get boxcars or hoppers, the interchange can handle any type of traffic.



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