Scheduled switching
To add to Mr. Baker's comments, typically the large customers are very few, the tiny customers are numerous. If I had to put numbers on it, less that 5% of customers (not cars) are large and probably 60-75% of customers are tiny. At least that was how it was back before the 1990's. After that the railroads put on a concerted effort to abandon unused trackage and pull up switches for tiny customers. On a 2020 railroad those percentages may no hold just because many of the tiny customers are physically gone.
On the railroad I worked for we didn't schedule the work that way (assuming I am understanding what Mr. Baker is describing), we basically had an area that the switchers worked every day they were scheduled to operate (depending on whether they were 5-6 or 7 day jobs). They switched every customer that had business in that area every day they ran. There were places with really low volume branches out of the same area where there might be a local that operated on different branches on different days of the week. Customers on some branches might only get switched once a week. There was a concerted effort to interchange every day a job ran.
I was actually part of a project to schedule rock train service in S Texas. Unit gravel trains would run from A to B on M-W-F and A to C on T-T-S. Dismal failure. It worked right up until the first time it rained and the pits became too muddy to mine rock. Then another road project got delayed a couple days, then a loader broke down, then a customer ordered an additional five trains. All issues that the railroad had no control over.
What customers "demand" and what customers get are not necessarily the same thing. Generally you can optimize around one major customer, the rest get switched when they get switched. If a customer on the north end of the branch and customer on the south end of the branch both want to be switched at 7 am, one of them is outa luck. The railroad can optimize one and the other one is just stuck. The switcher can't work two industries in different places at the same time.
As far as a switcher not wanting to have a load spotted on a Friday night, they don't understand how things work. This assumes its a railroad owned car, not a private car, because private cars (reporting marks end in the letter X) generally don't get charged demurrage. If you have a load to be spotted there are only four choices:
- Actually place (spot) the load, which starts the demurrage clock
- Don't spot the load, which will trigger "constructive placement" (CP), which starts the demurrage clock anyway
- Lease track space to store their cars, the car will be placed on the storage track, which starts the demurrage clock and they get charged a switch fee to spot the car later
- Negotiate a contract that gives extra time if the car is spotted on a Friday
Note that only one of them avoid demurrage charges. Plus if they say that they don't want to be switched on Friday night, so the railroad holds the car, then another car shows up and on Sunday or Monday, when they go to switch the industry, they can only spot one car, that extra car that the railroad has because the customer didn't want the previous one spotted becomes CP'd and goes on demurrage too. Back in the day, the local agent could just not charge the customer the demurrage or switching charges. But once the railroads computerized, that became waaaaaay harder to do. On the MP they said they paid for the development of their computer system in the first year or two just on the increased demurrage and switching charges they were missing before.
The other thing is is the job is working where its going to spot them around midnight, then on Monday, the switcher will spot them around midnight on Monday. So if they don't get spotted on Friday at 1130pm then they might not get spotted until 1130pm Monday when the local runs again, which means they will have all day Monday with nothing to load/unload. Just because they want to be switched on Sunday night doesn't mean they get switched on Sunday night. If they are the only ones who want a switch on Sunday night, the railroad isn't going to spend $1000 to spot a car they are going to get $100 profit on.
The whole "Just in Time" thing is generally only used by major shippers. No smaller shipper should ever expect JIT service from a railroad. Shipment times can normally vary two to three days. Other than major premium shippers (and certain huge bulk customers), there is no penalty for late shipments, there is no guaranteed shipping or transit time. Its a railroad, not FedEx or UPS.
For example the customer that doesn't want to be switched on Friday night. If they aren't going to be worked on Friday night, that means they aren't going to pulled Friday night either. That means an outbound load isn't going to move til Sunday or Monday when they are worked again. A car shipped on Tuesday will have a minimum of a 4 day transit (for example), while a car shipped on Friday will have a 5 or 6 day transit because the switching schedule is different. Compound that with schedules of trains operating on only selected days across the whole trip and cars can have wildly different transit times. Layer in maintenance curfews, weather delays, operational issues and incidents (failures, accidents, etc) and transit times are not going to be consistent.
A railroad can optimize on one or two services, but not hundreds on the same train (unless they have the exact same requirements) . For example railroads optimize UPS shipments. A train might have 20 cars of UPS. But in doing so, they sub-optimize the opposing 30-100 trains (with 3,000-10,000 cars) the UPS train will meet on its trip across the railroad. The UPS train goes screaming by, but everybody else sits in the hole and is delayed.