The trainee controller having to refresh his knowledge in double-line automatic signalling rules at the same time as undergoing desk certification complicated the desk certification process, requiring more handovers during a shift. There would be some safety benefits in KiwiRail’s training system for train controllers in specifying a maximum period for which new and returning train controllers can be away from using critical systems such as double-line automatic signalling before requiring refreshing in these systems. Trainee train controllers not being fully current in critical systems, or potentially experienced train controllers returning to using a critical system that they have not used for some time, is a safety issue.