A train … delivering value to the marketplace.

… highly prioritized valuable items are inside each container.
Each container has fixed cost and fixed capacity; however, what’s inside (usually what the marketplace demands for) can be anything … as long as it fits into the container… and the shipper can afford the cost if the container and agrees on the train’s schedule.
Yes, the train runs on schedule… and the schedule is published and available to everybody so they can plan their shipment accordingly.
And, yes, every shipper has a manifest for each shipment container.
That same spirit goes to SAFe’s Agile Release Train (ART)…
Think about it…
Do you see parallelism in terms of Highly-Prioritized-Value, Fixed Capacity, Variable Demand, Cost, Fixed Schedule (Planning Interval (PI)), Release Management (the manifest)?
There are many other ideas like this — short but sweet ideas — are found in over 60 topics in my new book, ‘SAFe (6.0) Is like …’ … available on Amazon… it has reached ‘# 1 New Release’ several times! Check it out.