Physics-based minecart trains link the world together. Couple carts behind a furnace engine, ship cargo between towns, and let the train load its own chunks while you focus on something else.
A train is a chain of minecarts pulled by a furnace cart. Couple them with chains, in order, behind the engine.
Example: Furnace → Cart → Cart → Cart
The furnace cart loads and unloads chunks as it moves. Trains can cross the world without anyone there to keep the chunks awake.
Laying track is no longer an iron-mine money pit.