The indicator shows the greenhouse gas (GHG) emissions from transport in the past. The total emissions are subdivided into road, air, rail and maritime transport. Emissions from international bunkers are not included.

The Kyoto Protocol considers six pollutants from the GHG group; namely carbon dioxide (CO₂), methane (CH₄), dinitrous oxide (N₂O), hydrofluorocarbons (HFC), perfluorocarbons (PFC) and sulphur hexafluoride (SF₆). Due to comparability, the GHG amounts are calculated to a CO₂ equivalent that considers the differences between the global warming potential of individual gases.

Mitigation of climate change is the biggest environmental development challenge facing humanity. Scientific results show that there is a connection between GHG emissions (CO₂, CH₄, N₂O and F-gases) and atmospheric temperature. Since the amount of anthropogenic greenhouse gases in the atmosphere is intensively increasing due to increasing emissions, primarily due to the energy consumption of fuels, there is a high probability of a temperature increase in the future. This would strongly influence life on Earth. Therefore, a campaign was commenced at the international level, the objective of which is to reduce GHG emissions to values that would have an »acceptable« impact on the environment. The Kyoto Protocol stipulates emissions for the period 2008–2012 with regard to emissions in the base year, which are for Slovenia defined as the sum of CO₂, CH₄ and N₂O emissions in 1986 (the base year for developed countries is 1990) and F-gases in 1995. The limitation of GHG emissions in Slovenia obtained a legal framework and specific objectives with the adoption of the Act Ratifying the Kyoto Protocol to the United Nations Framework Convention on Climate Change (OG RS, no. 60/2002).

At the 12th conference meeting of the contracting parties in 2006, negotiations on new objectives for the period after 2012 began. The leading role was taken over by the European Union, which adopted an objective in 2007 to reduce GHG emissions in 2020 by 20 or 30 % with regard to the base year. A 20 % reduction in emissions is required if the international agreement on the reduction of GHG emissions will not be adopted and a 30 % reduction in case of adoption of the international agreement.

According to the data of the Environmental Agency of the Republic of Slovenia, the largest share of GHG is contributed by the energy sector (81 % in 2007), of which energy supply contributes 34.1 %, followed by the transport sector (26.0 %). Transport GHG emissions in the period 1986-2007 more than doubled. Road transport emissions increased by 174 %, air transport emissions by 175 %; on the other hand, rail transport emissions reduced by 45 %. In the split of GHG in the considered period, N₂O emissions increased the most (almost by five times) due to an increased share of vehicles with catalytic converters, which reduce cars’ exhaust emissions of certain air pollutants but produce N2O as a by-product. CO₂ emissions increased by 162 %, CH₄ emissions have been slightly reduced. In the total GHG emissions in 2007, transport represents 26 %.

Road transport is the source of the majority of emissions, since in 2007 it contributed 99.2 % of all emissions. The number of road motor vehicles as well as the power and capacity of their engines have been constantly increasing in Slovenia, while the specific use of new vehicles has not been reducing (MESP, 2009a). The development of infrastructure, especially in urban areas, cannot follow such growth; therefore, congestions are becoming more frequent. In recent years, the increase in road freight transport, especially transit transport through Slovenia, is also a major problem. The share of transit freight transport emissions in 2007 was estimated to be 12 % (MESP, 2009). Otherwise, freight transport causes 37 % of GHG emissions, while other emissions are caused by passenger transport (personal transport 61 %, bus transport 2 %) (ARSO, 2009).

According to the data of the European Environment Agency, the emissions of GHGs from transport (excluding international air and maritime transport) in the EU-15 area increased in the period 1990-2007 by 24 % and in the new Member States (EU-12) by 46 %. According to the growth of emissions, Slovenia is positioned in sixth place of 32 countries, which are members of the European Environment Agency. In the older Member States, the growth in emissions has stabilised in recent years, while in the same period the growth was significant in the new Member States. Road and air transport contributed to this growth; also GHG emissions from international aviation and navigation are increasing rapidly, but these emissions are not included in the GHG emission totals relevant for the Kyoto targets (EEA, 2009).

For the fulfilment of the Kyoto Protocol Commitment, the Government of the Republic of Slovenia adopted in 2003 (with amendments in 2004) the Operational Programme for Limiting Greenhouse Gas Emissions. In 2006, a new programme was adopted, supplemented and amended in 2009. In the last version, the Ministry established, similarly as is the case in the programme from 2006, that the emissions of GHGs from transport in Slovenia are on a critical path, while their control is of key importance for the fulfilment of Kyoto commitments. Especially worrying is the transit of heavy trucks through Slovenia, which has strongly increased since the integration of Slovenia into the EU. The measures to reduce transport emissions are the following: the reduction of emissions from passenger cars, promotion of public transport, sustainable freight transport and the replacement of fossil fuels with biofuels. Since the implementation of measures of previous operational programmes was insufficient, Slovenia will not be able to achieve the Kyoto objective only by domestic measures; therefore, the Operational programme stipulates the use of the Kyoto flexible mechanisms. This consequently means a need to provide funds from additional taxation of engine fuels (MESP, 2009).

Forecasts of the developments of GHGs from transport in the last Operational Programme for Limiting Greenhouse Gas Emissions were, in accordance with the past trends, corrected. Their volume will increase in 2008; in 2010, it is expected to decrease due to the economic crisis. Average emissions in the period 2008–2012 were estimated to be 6.165 kt CO₂ eq., which is 14 % more than in 2007 (MESP, 2009).

The efficiency and adequacy of the measures of the operational programme are uncertain, especially since the state is not implementing an integrated transport policy, which would harmonise the transport system and enable a more equal development of sustainable transport modes. Since there is no efficient transport policy, the planned measures with regard to public transport and an increased share of railways for the transport of cargo and passengers are at issue (MESP, 2009a).