What is a tonne-kilometre?

One tonne of goods moved one kilometre. Twenty tonnes moved 800 km is 16,000 tonne-km, and multiplying by a factor in kg CO2e per tonne-km gives the load's emissions.

Which freight mode has the lowest emission intensity?

Per tonne-km, in the UK's 2026 averages: container ships (0.016 kg CO2e), then rail (0.026), then articulated trucks (0.079); long-haul air freight is 0.53 without radiative forcing.

Should air freight emissions include radiative forcing?

That is a reporting choice; state which you used. The UK set publishes both, and applying the indirect effects raises the CO2 factor by about 70%.

Term

Emission intensity (freight)

Emission intensity is the greenhouse gas emitted per unit of transport work, usually grams or kilograms of CO2e per tonne-kilometre — one tonne moved one kilometre. It lets loads and modes be compared: UK 2026 factors put an average laden articulated truck at 0.079 kg CO2e per tonne-km and a freight train at 0.026, tank-to-wheel.

Also called carbon intensity of freight, gCO2e per tonne-km, emissions per tonne-kilometre, kg CO2e per tkm, tonne-km emission factorUpdated 13 October 2026

By mode

Mode	Tank-to-wheel	Well-to-tank
Rigid truck, average laden	0.19947	0.04332
Articulated truck, average laden	0.07926	0.01823
All trucks, average laden	0.10356	0.02359
Freight train	0.02583	0.00691
Container ship, average	0.01612	0.00365
Long-haul freight flight to or from the UK, without radiative forcing	0.5313	0.13516
The same flight, with radiative forcing	0.89939	0.13516

UK DESNZ greenhouse gas conversion factors 2026, kg CO2e per tonne-km

The GHG Protocol's technical guidance describes these as distance-based factors, typically in grams or kilograms of CO2e per tonne-kilometre or TEU-kilometre. US factors use short ton-miles: the EPA's 2025 hub gives 0.186 kg CO2 per short ton-mile for medium- and heavy-duty trucks, 0.021 for rail, 0.077 for waterborne craft and 1.086 for aircraft. Radiative forcing — the extra warming from aircraft emissions at altitude — is why the UK's with-RF air factor is about 70% higher.

Worked example: one load, road or rail

20 t × 800 km = 16,000 tonne-km · artic: 16,000 × (0.07926 + 0.01823) = 1,560 kg CO2e well-to-wheel · rail: 16,000 × (0.02583 + 0.00691) = 524 kg — about a third

UK DESNZ 2026 averages. A real train or truck may be fuller or emptier than average, which is why fuel-based figures, where available, are more accurate.

The mistake people make

Using the wrong denominator. The UK set publishes factors per vehicle-km beside the per tonne-km ones and warns users not to confuse their purpose; the EPA advises vehicle-mile factors when the whole vehicle carries one company's goods, and ton-mile factors when it is shared with other companies' freight. The GLEC Framework asks for both numbers, total emissions and intensity, so a falling intensity cannot hide a rising total.

FAQ