passengerkilometres

Passenger-kilometres (PKM) is a transport performance metric representing the total distance traveled by passengers. It is obtained by multiplying the number of passengers by the distance they travel and is usually expressed in passenger-kilometres. PKM measures the volume of passenger traffic across a transport network and is the passenger analogue of tonne-kilometres used for freight.

Two common variants are used in statistics: total PKM, which counts all passenger travel, and revenue passenger-kilometres (RPK), which includes only travel for which a fare is paid. In practice, PKM can be calculated by summing, over all trips, the product of the number of passengers on the trip and the distance traveled. For a service with P passengers covering D kilometers, PKM increases by P×D. For multi-leg journeys, PKM sums the distances of each leg traveled by the passenger.

PKM is widely used to assess demand, compare systems, estimate load, and support planning and policy. It is foundational for calculating related metrics such as the load factor (RPK divided by available seat-kilometres) and is often normalized by population or GDP for mobility analysis. It also informs energy intensity and emissions assessments tied to passenger transport.

Data for PKM come from ticketing records, passenger counts, and automatic passenger-counting systems, sometimes combined with surveys. Limitations include variations in counting methods across modes and the treatment of transfers or free passes, which can affect comparability with RPK or SKM-based metrics.