Averaging. “To ‘average’ means that separate calculations are to be made for loading and discharging and any time saved in one operation is to be set against any excess time used in the other.” (Charterparty Laytime Definitions 1980)
(Note that this meaning of “average” is very different from the meaning given to it in “General Average”.)
The options of averaging laytime and of using “reversible laytime” are options to the charterer, for whom each method has advantages over a method where demurrage and despatch are separately calculated and paid. Usually the rate of despatch is half that of demurrage.
“Reversible” means that an option is given to the charterer to add together the loading and discharging laytime as if one reservoir of laytime is allowed for both operations.
It is clear that if an option to average is given in the charterparty the charterer would take advantage of it, especially if he controls the cargo-handling operations and is likely to earn despatch on all time saved.