10-25-2011, 11:16 AM
Typically railroads don't repaint freight cars unless they get major repairs. They may not even bother to "patch" a car in the event of a merger beyond changing the reporting marks and car number if necessary. I think 40 years is how long a car is allowed to remain in revenue service before it is either retired, transferred to non-interchange service, or rebuilt. Logically then, the more years that have passed since the merger, the fewer cars in the pre-merger paint schemes will show up on a train. The closer you get to 40 years post merger, the more likely that pre-merger paint schemes will have disappeared.