CartLoad
A tiny mod that makes minecarts dynamically chunkload their surroundings, but only if they're in motion.
This mod is completely standalone and does not require any of my library mods. It also does not require any manual configuration. Just drop it into a server, and it works.
(Compatible with RailCraft)
Purpose and explanation
Compared to classical chunkloader carts, these minecarts stop their chunkloading activities when they stop moving. This dynamic chunkloading system prevents some odd bugs with minecarts disappearing or duplicating at chunk borders, caused by race conditions when chunks get loaded/saved to disk. By force-loading the current chunk, and the chunk the minecart is about to enter, these race conditions can be completely avoided by always having the relevant chunks actively loaded. This chunkloading also persists between restarts, so minecarts that were in motion stay in motion when the world is reopened, even if they're not in the vicinity of any actual chunkloading mechanism.
NOTICE TO SERVER ADMINS AND MODPACK DESIGNERS
This mod can be easily exploited as a way to achieve unlimited chunkloading for no cost, only use this mod on servers where the players can be trusted not to abuse the functionality. The primary use case for this mod is RailCraft-focused megabases and long range networks, without having to keep the entire rail line constantly chunkloaded.