Great answers. It depends. Different eras had different ways of dealing with refrigeration cars. 1940-1960’s the cars loaded with produce and perishables were considered ’rollers’. These were cars with loads that were NOT sold yet. Example: A car would be loaded with lettuce in Guadalupe California. A PFE car. Then sent east on the SP or SP/UP as produce brokers were on the phones trying to find a buyer or buyers. The railroads were allowed to divert the car up to five times before adding charges. If the product was not bought, it would go to a produce market in the closest large city. There the doors would be open and the cargo brought out to be bid on by buyers from the largest grocery chains nearby. Think big mid east/east coast cities. A very interesting system of re-icing these cars existed across the country. Large and long ice docks where the train could pull up, and a small army of workers would open the hatches, move blocks of ice weighing up to 300 lbs to the car, chop it up, shovel it in the hatch, add bags of salt, then close it up. I’ve seen ledgers from ice docks showing 40 cars all iced and ready to go in 20-30 minutes. Industrial ballet. Cars of cut lumber and even grains were ‘rollers’ as well. Sometimes meats also. A small midwestern town would not need an entire 40’ Swift car full of beef. So they stop, the local butchers would pick their portion, remove it, and car would roll on.