Callback: Wagon length
From GRFSpecs
Jump to navigationJump to searchWagon length (11)
GRFv8 This callback is only called for GRF version 7 and below. For GRF version 8 and above use callback 36.
This callback is used instead of property 21 whenever the train leaves a depot or is displayed inside a depot. If the callback fails, the value of property 21 is used instead.
Road vehicles do not have a property for this purpose. If the callback fails, a length of 8/8 is used.
The callback result may change only when whole vehicle chain is inside a depot.