The modelling of externalities from transportation focus on emissions and congestion. This means that other externalities, such as accidents, noise and wearing of infrastructure are not included in the sub-model. While the emission of greenhouse gasses and other pollutants are the result of fuel consumption, accidents, noise, wearing of infrastructure and congestion are mostly caused by the traffic volume. The reason for including congestion, and not the other externalities cause by traffic volume, is that firms and households not only face a direct monetary cost of transportation, but also the cost related to spending time in traffic. This is, for example, important when analyzing the effect of environmental and climate-related tax reforms, since households’ labor supply is closely related to their time spent commuting.
The modelling of emissions from transportation focus on energy-related emissions of greenhouse gasses and other pollutants. Upstream emissions from the production of vehicles are not modelled explicitly in the transportation sub-model. This is due to the fact that most vehicles in Denmark are imported from other countries, implying that emissions from the associated production process are not counted as emissions from Danish economic activity. The chosen energy-related emissions are:
- Greenhouse gasses (methane, nitrous oxide and carbon dioxide)
- Particulate pollution
- NOx (nitric oxide and nitrogen dioxide)
- Sulphur dioxide
Finally, the sub-model does not account for international transit through Denmark, since there is not sufficient data to to say anything about the scope of this. The transportation sub-model does, however, include emissions from Danish-owned vehicles overseas. These are included because a significant share of emissions from Danish-owned vehicles occurs outside of Denmark, due to the size of the Danish shipping industry.