Revenue passenger miles (
RPMs) and
revenue passenger kilometers (
RPKs) are measures of traffic for an
airline flight,
bus, or
train calculated by multiplying the number of
revenue-paying passengers aboard the vehicle by the distance traveled. On long-distance buses and trains (and some planes) passengers may board and disembark at intermediate stops, in which case RPMs/RPKs have to be calculated for each segment if a careful total is needed.