Once a year, Silicon Valley Lines does an inventory of all rolling stock to ensure that we know which cars are present on the layout and the actual location of each car is consistent with where the computer thinks it is. With 1300 cars on the layout this is a lot of work for our train master, so a few folks helped out.
How can it be that cars are not where they are supposed to be, you ask? Simple. We’re all humans. We make mistakes. We take an extra car on a train we’re not supposed to. We forget to take all cars we’re supposed to. Sometimes a planned train doesn’t run as scheduled for a variety of reasons. For operating layouts using computer-based paperwork, this drift between reality and what the computer thinks is quite common. Here are all the cars I found in Nowheres and Jasper Jct that didn’t belong. This is quite a bit more than expected. We determined that one of the freights from Nowheres to Bakersfield must not have run in a recent session.
By the way, layouts using car cards & waybills have similar problems where due to human error the pairing between car card and car is lost, resulting in cars without a card, or cards without a car. On small layouts this is usually resolved easily and quickly, but ends up being just as much of a challenge on large layouts, and owners usually have a system to keep things in sync.