This program moves cars around your layout in response to customers requesting that a shipment of goods be picked up for delivery. That's what is simulated here. Thus this program is deeper than just commodity based shipments to shipments of specific goods. Sounds like this will be more detailed, and hence more complicated, but this program is designed to keep that complexity hidden. Indeed there is much to enter to create a shipment, but this creation of shipments, and management of those shipments, is as simple as could be made. See Creating Shipments for how to actually create shipments. Here the discussion will be around the philosophical issues of shipment based car routing.
There are as many different methods to route cars on your layout as there are layouts. A number of specific methods are predominant, such as commodity based, or car type based, shipments. Details of these can be found elsewhere. This system is based upon the commodity method with a twist. This program is based upon a shipper sending goods somewhere else. It is done on a per commodity, per car type, per day basis, but it is a shipment from an industry to another industry.
There are three types of industries this program can use. First is a standard, what you would think of, industry. Some factory or depot, that ships goods out to some other destination. The second type is an interchange to another railroad. An interchange is a portal to the outside world and allows shipments to head off the layout to some other far away destination. This program does not care about the actual location name, only that to get off the layout it must go through this interchange. Interchanges can also bring goods onto the layout. Thus, when you create shipments, you can select an interchange as an "Industry" that ships to somewhere on your layout, or off at some other interchange. You can also make shipments to an interchange, as if they leave the layout. The third type of industry is a yard. You can designate any yard as a portal to the world. Thus you can make shipments to and from any yard you want to indicate as such. By definition staging and fiddle yards already are portals, thus they will automatically become industries to ship from and to.
You do not need to make a "shipment" of an empty car to start a shipment, that is handled automatically.
Shipments are on a per car type per commodity basis. That is, not only do you need to know the car type an industry will ship it's goods in, but the commodity that the car can carry. By default the program has a commodity of "anything", which if you want, you can just use this. That's the simplest method. You can define your own commodities, assign them to cars, and use them to fulfill shipments. However, there comes a warning with this. See Assignment Limitations for more on this, but basically it comes down to you need to make sure you have enough cars that can carry the commodities you define to fulfill the shipments you make that will use those cars. It's no big deal to not have enough, it will just mean that certain shipments will not always happen when they should. (The program does not store these to try and run later, as that would just compound problems) There are a number of displays that will help you set things up with this regard. You should also note that you can also define secondary commodities, any number you want, to any cars you want. After a primary search for the right car is not found, secondary commodities will be searched.
Shipments also have a frequency attached to them. This frequency is one of the following: Random, daily, day of the week, day of the month, and one time.
For Random shipments you can set the probability that the shipment is to be done from 10% to 90%. This is based upon when a train visits the town the industry that wants a random shipment resides. Every train that does switching at that industry will be checked for random shipments, which in turn will have it's probability calculated. Should the shipment "win", it will be added to the switch list.
Daily is just that, every day you run a train to switch an industry with daily shipments will get that shipment done (subject to the right car being available).
Day of week you pick a day of the week to start the shipment. If you want one shipment on Mondays, another on Wednesdays and another on Fridays, simply create a new shipment for each of those days. You can do this easily by creating the first one, select it, change the day, and then create as opposed to update.
Day of the month means you pick a day of the month and do the shipment then. For more than one, do the same as noted above.
One time shipments are just that. They happen once and never happen again.
One thing you must note about the frequency of shipments. When you set a shipment to occur on a Monday, that is not when the full car leaves the industry. It simulates when a call is made from that industry to send them an empty car for filling. Thus the Monday is when an empty will be sent to that industry. Only after it's arrival does it then stay to be filled. If you have indicated that it takes 5 days to fill, the earliest the car can move out full is the Friday. But the empty might not get there on the Monday. If no suitable empty cars is available at the train's starting yard, then elsewhere on the layout needs to be checked. If the only available car is at a different yard, it might take a day or two to get to the industry that needs to ship out.
You also have the option of making a shipment happen based upon the season. You have two choices, All Year, or any one of the four seasons. Thus if you want to ship apples only in the Fall daily you can do that.
Certainly the more variability to give in the shipments the more fun and combinations you will have. There is a price for this. The more complexity you invoke for your shipments, the more the likelihood that a shipment will not happen for what ever reason. Don't be quick to blame the software if your daily shipment from the cattle ramp is not happening, it just may be that you do not have enough cars to begin with.
There are a number of displays to view you shipments from different angles. The two you will use the most is the Industry by Frequency list and the Flow list. They are both discussed in detail in Managing Shipments.