Do free wagons always need 500 items to depart?

No. The current initial free-transport minimum is 1,000 and can be changed in the station window. The ordinary fixed-route source-loading minimum is a separate parameter, initially 50. Free transport also checks a planned receiver's shortage or a source's available surplus against its minimum. Shortage, surplus and vehicle capacity are different tests; low-stock exceptions in other transfer branches do not apply to every free-wagon task.