Multiple Identity Maps (MIMs)

Running a multiple-identity map (MIM) takes more thought than running a single-identity map. The usual reason a map gets set up as a MIM is that there is more than one RR in the same geographical area, and making the operations work smoothly requires keeping those railroad identities separate. So, if you are asking "how do I run a MIM map?" you are really asking "what tools does FYM have that allow me to keep operations of the two RRs separate?"

Choosing how to route outbound cars is the most basic function a YM does in FYM, and in a MIM, the choice on route out of the map depends on which RR that car is on. YMs always need to develop an operating plan for each map, and with MIMs you simply make that plan for each map identity. If you do that, the choices about car routing are much clearer--they become essentially no different from a single-identity map. However, you need to keep track of which RR is which and what traffic belongs to each RR.

Here is how I set up my operations on a MIM:

1. I always start my orientation to a new MIM by clicking on each siding and determining which RR serves which industry. Sometimes more than one RR serves a single industry, which adds complication, but there are tools available for that.
2. Next, build color filters (shift-3/4/5) for each RR. You do this by the usual method of consulting the tsars database and figuring out which symbols work your map and what jobs they need to do, which also determines how you route outbound cars, and setting up sort filters to handle those cars. The trick is for MIMs you need complete sets of filters for each identity. FYM allows you to do that by allowing you to create "Display Sets" where it only uses some of the sorts you define at one time.
3. Finally, set up a filter to allow you to distinguish cars by their source. There are two ways to do this: sort display sets (shift-3/4/5 filter) that use the "only for cars to/from" feature, or you can use the number-pad filters to display car colors according to the location the cars were last unloaded or loaded. By using numpad-3 on cars you are picking up from local industries, you can easily see which of your map IDs originated the car, and thus which RR should be handling it outbound. You may need to set up your 3 filters if you don't already have unique colors for the IDs in your MIM. Alternatively, you can use the numpad-6 filter as a quick-and-dirty way to tell originating roads apart if that's all you need to do.

Car origin is often just as important as car destination when choosing how to route cars from MIMs.

Being a good MIM YM requires you to learn about using filters to identify car origin and use them in your normal operations.