Tonnenkilometer

Tonnenkilometer, in English commonly written as tonne-kilometre (tkm), is a unit of freight transport work. It represents the movement of one metric ton over a distance of one kilometer. This measure is used to quantify the amount of freight moved and the distance it travels, enabling cross‑modal comparisons of transport activity.

Calculation and example: tonne-kilometre is calculated by multiplying the mass of goods (in tonnes) by the distance moved (in kilometres). For example, transporting 5 tonnes over 200 kilometres equals 1000 tkm. If two shipments of 2 tonnes and 3 tonnes travel 150 kilometres each, the total is 2×150 + 3×150 = 750 tkm.

Applications: this unit is widely used in transport statistics, energy and emissions accounting, and logistics performance assessments. It helps analysts compare freight activity across modes (road, rail, water, air) and over time. International organizations such as Eurostat and the OECD use tonne-kilometres to report freight performance and to analyze trends in trade and supply chains. It is also used to compute emissions or energy intensity per tonne-kilometre.

Limitations: while tkm captures volume and distance, it does not by itself reflect energy efficiency, load factors, empty haulage, or cargo characteristics. Therefore it is typically used in combination with other indicators, such as energy use or greenhouse gas emissions per tkm, to assess overall freight efficiency and environmental impact. A related unit is tonne-mile, with 1 tkm equal to approximately 0.621 tonne-miles.