Two seprate timetables on the KWVR Leslie. The steam is running for pre-booked passengers and the DMU shuttling back and forth all day. If John gets a day rover ticket he won't need to get off at all, there's a 3 minute turnaround at each end of the line each trip, meanwhile the steam is going in the opposite direction.
http://www.kwvr.co.uk/santaspecials.html
Are you sure that the 20,000 punters is one days worth? Most galas at places like the SVR only have about 6000 over a three day weekend, 20,000 sounds like the Santa season total to me.
Regards, 62440.