passagerkilometers

Passagerkilometers, often abbreviated PKM, is a transport metric used to quantify the total distance traveled by passengers. One PKM equals one passenger traveling one kilometer. In practice, PKM is calculated by summing, for all trips, the product of the number of passengers on the trip and the distance traveled.

PKM is widely used to assess demand for passenger transport and to compare performance across modes such as road, rail, air, and sea. It supports planning, capacity management, and policy evaluation, and it is used in calculations of energy intensity and emissions per PKM (for example, grams of CO2 per PKM) to gauge environmental impact.

Data for PKM can come from ticket sales, passenger counts, surveys, or integrated transport models. Distances are typically route-based and aggregated to the network level; PKM can also be calculated for specific modes, routes, or time periods. PKM is useful for benchmarking and trend analysis, and it can be reported at national, regional, or operator levels.

Limitations include that PKM does not directly reflect service quality, crowding, or the distribution of trips, and it can obscure low occupancy in high-frequency corridors. It should be complemented with other metrics such as revenue passenger miles, passenger trips, occupancy rate, and vehicle-kilometers to provide a fuller picture of performance and efficiency. Related concepts include ton-kilometers for freight, and various per-capita or per-seat measures used in transport planning.