This is an example of how things work:
Day One:
The Walmart distribution center in Casa Grande, AZ notifies ACME Food Products in Buena Park, CA that they require replacement of sauces sold in the area stores.
ACME Food Products picks the products from the racks in their warehouse and notifies Streetway Trucking in La Mirada, CA that they will require a pick up.
The Streetway dispatcher notifies the Pickup and Delivery driver in the Buena Park run of the pickup.
THE ACME warehouse men palletize and wrap the products onto six pallets.
The Streetway driver picks up the pallets on his way back to the terminal.
The Streetway dock workers unload the pallets and load them onto a trailer destined for their Phoenix terminal along with many other shipments from and to many other customers.
A Streetway line driver hauls the trailer to Desert Center, CA where he swaps the trailer with a trailer headed for la Mirada brought there by a Phoenix line driver.
The Phoenix Streeway driver hauls the trailer brought by the La Mirada driver to the Phoenix terminal.
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Day Two:
The trailer arrives at the Phoenix Streetway terminal.
A Phoenix dock worker unloads the pallets and loads them into the Casa Grande run trailer.
The Casa Grande run P&D driver hauls the trailer to the Casa Grande Walmart distribution center.
The P&D driver sorts and segregates the cases of sauce.
A Walmart distribution center receiver checks the products in.
A Walmart fork lift driver puts the product up on the racks in their proper places where it is ready to be shipped to a Walmart store PERHAPS THAT SAME DAY.
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Can rail freight respond like that?
Your schedule looks to me as if everyone is working 12 hour days. I’ve seen all that take place in 36 hours or less.
If I were allowed to choose between (a) not having trucks clogging the interstates 24-7 and (b) having everything in my local stores available whenever I want it, it would be an interesting choice, and one which Americans should be allowed to contemplate. As it is, I think we are getting neither.
This system does not seem to be working for the Walmarts and Krogers in my town as you postulate it does. In the last year, far more than in the past, I am seeing some popular and high-demand products missing from the shelves for days on end.
I suspect that the concept of "just in time" is proving to be as dodgy for the retail business as it turned out to be for my healthcare company, where "just in time" has been replaced by "be mindful of a potential shortage".