Now that we have sorted out how the main functions of the Decision Engine (DE) work, it is time to look at the customer demands. These are what drives the railroad after all.
The local meat packers has a stock car of beef due from Chicago. Once this has been handled, they need a refrigerator (reefer) car to take out some of the produce whilst two box cars are needed to take the rest of their week’s production.
All references to locations and industries are those located on the test layout shown earlier. Chicago is to the west of the railroad so a loaded stock car would be brought on an east bound freight to Hartford. The next freight train due from Hartford will bring it to Sunset. Staging (See the glossary below) has a special rule for allocating cars which will be discussed later.
The stock car is easy. We create a demand from the packers, which is resolved by allocation of a stock car on the Hartford staging. Empty box cars come from the general pool so can be sourced from either end of the railroad. The reefer is required to be cold (in these times, reefers were loaded with blocks of ice to chill the interior) so would have to be sourced from the Ice House at Sunset. Thus, a request for a reefer actually causes one to be allocated to the Ice House for at least one half of a day before it can be shipped to the meat packers. Again, if a reefer should not be at Sunset, an empty one would need to be sourced from either end of the railroad.
This makes three different types of action, all of which have to be allowed for in the DE. Another type of operation would be typically needed by coal mines, for instance. An empty hopper is delivered to the mine and then loaded. Loaded hopper may well ship to multiple destinations. However, this operation is empty driven whilst one of the operations mentioned above is load driven. This is a crucial distinction in the DE.
Staging – parts of the railroad designated as “off scene”. They are normally used to represent other destinations and normally comprise one or more straight tracks out of sight to be used to store trains. In our test layout both Hartford and Boston are represented by staging. In our test scenario,they are actually one and the same staging tracks. Because they can be switched (shunted) by the “big hand in the sky”, it could be permissible that any of scene freight car can be sourced from any staging destination. On larger railroads, this would not necessarily be true.