Methodology for GHG Efficiency of Transport Modes

Fraunhofer ISI and CE Delft, on behalf of the European Environment Agency (EEA), developed a methodology for determining the greenhouse gas (GHG) efficiency of the transport modes road, rail, aviation, inland navigation, and maritime shipping. The indicators relate to both passenger transport (GHG emissions per passenger kilometre) and freight transport (GHG emissions per ton kilometre).

In a pilot application, using the developed methodology, the project partners calculated the indicators for the years 2014 to 2018 for the territory of the European Union (EU-28 and EU-27 excluding the United Kingdom).



The study objectives were to establish a robust and dynamic methodology for a continuous set of indicators for the transport sector, measuring and tracking the GHG efficiency in European transport. In this respect, it continues the work done by EEA, the European Commission and other institutions in the past. Points of departure for this study include the EEA GHG Inventory, progress indicators in energy efficiency, average CO2 emissions from newly registered motor vehicles or the European Union's regular updates on the external costs of transport. The methodology developed reflects the current state of knowledge in emissions reporting, is designed to be replicable by the EEA, and is consistent across modes to enable comparison between modes.



In a first step, three transport markets for passenger and freight services in their regional context are defined: urban, rural, long-distance and extra-European trips and shipments. In these markets, GHG efficiency is driven by three factors: the energy intensity of fuels or electricity, vehicle power train technologies and load factors.

The following vehicle categories and market segments per main transport mode are addressed:

  • Road: passenger car, bus and coach, light duty- and heavy goods vehicles.
  • Rail: Conventional passenger trains, high speed rail, rail-based urban public transport and freight services.
  • Aviation: Civil passenger and freight traffic, excluding small emitters, such as light and sports aircrafts or helicopters.
  • Inland navigation and maritime shipping, including short sea and ocean freight shipping, coastal passenger ferries and cruise liners.

A more detailed level of analysis allows for differentiation by basic fuel types, such as petrol, diesel, electricity, kerosene, marine gas oil or heavy fuel oil.

The top level of analysis generates European figures by weighed country values for road, rail and IWW, and by using international data sources for aviation and maritime shipping. Results are shown as indicators for Europe as a whole and not for individual countries. The European scope, however, is kept flexible to allow adding or removing of single countries. In particular, we allow for the removal of UK data. The methodology also allows the inclusion of non-EU countries like Norway and Switzerland. National level data is used for internal calculations where needed, e.g. where European data is not reliable or not available with regular updates.

For aviation and maritime shipping the geographical scope is expanded beyond the European territory in order to capture emissions of entire voyages. In many cases emissions occur outside national territories and as a result these emissions can become unaccounted for. A method to overcome this issue is to allocate emissions and transport performance equally between the country of origin and destination.

In this study we apply a well-to-wheel (WtW) approach to estimate specific GHG emissions from transport modes. This means that emissions from the exhaust (tank-to-wheel) as well upstream- or well-to-tank (WtT) emissions are included. WtT emissions originate from the extraction, transport and refinery of fuels, including fossil fuels and biofuels. For computing TtW emissions the energy content method applies.

The pilot indicators presented in this study include the most recent years with sufficient data availability. Current data covers the period from 2014 to 2018 across all modes.


For the main transport modes on a European scale we find that passenger cars and domestic aviation have the highest GHG emission factor per passenger kilometre. However, aviation efficiency improved substantially by 11 % over the period 2014 to 2018, while the specific GHG intensity of car travel declined by 3 %.

Rail travel (with an improvement of 13 %) shows a similar pattern to aviation, although the reasons for higher efficiency are different. While aviation profits from higher occupancy rates possibly pushed by low cost airlines, the rail sector made significant progress in replacing diesel with electric propulsion. The decarbonisation of electricity production accelerates the positive effect of the electrification of rail transport.

A negative trend is observable with buses and coaches. Here the per pkm emissions increased by 12 % from 2014 to 2018. This is due to declining occupancy rates on long-distance buses. Low cost airlines and ridesharing offers for private cars may play a role here, as well as the rising number of long-distance bus connections.

Freight transport efficiency rates show much wider differences than efficiency rates in passenger travel. Emission factors in air freight is about eight times above those for heavy goods vehicles. Air freight is characterised by high value and time critical goods. Here, transport time considerations dominate and the GHG efficiency of the transport chain is correspondingly low. Due to the high share of belly freight, however, it is difficult to correctly split emissions between passenger and freight transport.

On the other end of the scale we see maritime shipping with 5 %, rail with 18 % and inland navigation with 24 % of the average per tkm GHG emissions of HGVs.

Improvement rates on GHG emissions per tkm over the period 2014 to 2018 for the EU-27 are highest for air cargo (14 %) followed by rail freight (11 %). HGVs show a slight improvement of 3 % specific GHG emissions.


  • July 2020 to November 2020


  • European Environment Agency (EEA), Copenhague


  • PCE Delft, The Netherlands
  • Ramboll, Copenhague, Denmark
  • Fraunhofer ISI, Karlsruhe, Germany