Re car quantities in RER
Can I suggest using RERs to determine the quantity of any railroad equipment at a particular time is subject to a lot of error?
If a series of cars is due to be taken off the roster due to age or rebuilding, there is no need for a railroad to “count down” the number of cars in a series with any accuracy. For example, if car in a series was scrapped, it could never appear in interchange. No clerk would look in an RER and care there were XX number of cars still in service, they would only be looking for the data on the specific car number they were concerned about. All they would be looking for is the car series that single car comes from to determine the Capy, etc. they needed to know.
The Southern’s practice seemed to be to modify car quantities for cars in service but stop making RER changes if they decided to take that series out of service. Rather than try to keep changing continually declining numbers, they would wait until none were left and delete the entire series.
The reverse was also true, cars could be in the RER that were not yet on the roster. They would never be seen in interchange so there would be no problem. Because cars had to be in the RER before they could be interchanged, the entry needed to be in place before they were delivered or in service.
In at least one Southern Rwy case, a series of cars was in the RER that never existed. The plan was for a group of 40 foot box cars to be given 70-ton trucks and renumbered. That group of cars existed twice in the RER, once under their original number series and also with their new 70-ton capacity numbers. For whatever reason, the 70-ton trucks were not purchased. Some repainted/renumbered cars had to be changed back to their 50-ton road numbers.
RERs are a good, widely available resource but we need to be careful using them to answer questions they were never intended to deal with.