Back in 1991, I was working on mechanisms for the bracket llayout. '"Real" operation on a single yard of track? Difficult, but not impossible', I wrote. For years, I've had a version of the sliding blocks puzzle on my laptop, allowing me to sort "loads" into sets, each set disappearing as it was completed. This wasn't my idea originally, Tony Koester of Model Railroader once described how a friend used it for filling an ore-freighter on his large layout - I just stripped it down until I could write a simulation.
Ria moved along between two hoppers, a and b, which held mixed yellow and green blocks. It delivered them to two tins, one for green and one for yellow. It was fascinating to watch and when I thought about it in detail, this is as complex as much "realistic" operation gets.
All I needed was an industry with several different loads and haulage paths, and then I could adjust the simulation and the Ria algorithms to fit. Now, I had little idea about how oil-shale extraction was managed at the site, but assumed that the shale was pounded up, put it into a retort and heat it.
So, I assumed transferring shale lumps inwards either to the furnace or the stamp mill. Processed shale went from the mill to the retort. Barrels of oil from the retort and waste from the retort and furnace were the outward loads. This was the basis from which I worked in 2003 when designing the reworked "Cuddle" protocols.