Modelling what might have been in southeast BC and northwest Wasington

Car attribute priorities

Some thoughts on the relative importance of various car attributes that can be considered when restaging cars.

The issue came to light during a phone call I had with Colin about his waybills and how he selects them for a particular car. I need to try to duplicate the mental process he goes through when resetting the layout, if at all possible.

At the moment, I have identified the following attributes, or characteristics, of a car that can be used when selecting a new role for them in staging. The list now includes the reporting mark initials and number, plus the owner railroad. I have listed them in a suggested order of most important to least to be considered when matching a car to a role, along with one sample for each attribute. Note that not all attributes will apply to one specific car. Most obvious is a gallon capacity for a boxcar. But, they are all available to be used as appropriate. 

  • – Initials: CP
  • – Number: 123456
  • – Type: Box
  • – Length: 40
  • – Subtype: Insulated
  • – Class: Rough
  • – Door: 8 feet
  • – Capacity: 6000 gals
  • – Owner: CPR

The order of these has some significance when we consider what to do when there is no match. The current program can handle a sequence of either-or values so that more than one attribute value can be considered to be a match. For example, the car length spec can be shown as “40|50” which means either a 40 foot or 50 foot car is acceptable and will match the role.

But what happens if no roles match a car that needs to be restaged when using this approach? Colin said that he often has to “substitute” cars for waybills so that the car can remain on the layout and have a role to play. We obviously want this substitution to be as close a match as possible, and as an example we will readily substitute a 6 foot door for an 8 foot request, as that will be barely noticeable. However, substituting a tank car for a box car would not be a good idea! So obviously some of the different attributes have more importance than others, with the primary car type being very important.

My idea for the program is that if a match can’t be made, then a second pass will be made, this time ignoring one of the less important attributes. If still no match, then we repeat this process until we have gone as far with substitutions as we are willing, and give up and store the car. It is this ordering of importance that I am trying to figure out.