1. Introduction
Sustainable transportation gains a lot of attention in today's research and practice. Economic growth and global trade relations lead to a tremendous increase in transportation activities. Transportation is related to numerous negative external effects such as noise, air pollution, or accidents; it is also a major contributor to human-induced climate change. Sims et al. (2014) state that greenhouse gas (GHG) emissions in the transportation sector have increased by a factor of 2.5 between 1970 and 2010 worldwide; hence, they have grown at a faster rate than in any other energy end-use sector. Victor et al. (2014) show that the transportation sector was responsible for more than 14% of the total global GHG emissions in 2010. GHGs include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs) (EU, 2017).
With regard to sustainable development, there is a vast array of definitions, terms, approaches, concepts, methods, and tools, many designed for specific fields only (Missimer et al., 2017). Johnston et al. (2007) estimate that about 300 definitions for sustainability and sustainable development exist. Commonly used are the three pillars or dimensions of sustainability: economy, ecology, and society. The Renewed Sustainable Development Strategy of the European Union adopted by the European Council in June 2006 defines a sustainable transportation system as one that āmeets society's economic, social, and environmental needs whilst minimizing its undesirable impacts on the economy, society, and the environmentā (EC, 2011). The authors of this chapter refer to this definition, when writing about sustainable transportation. Ongoing developments in vehicle technology, new organizational forms in transportation, investments into infrastructure, the internalization of external cost, or customized algorithms for transportation planning are vital, inter alia, to support the aim of having a sustainable transportation system.
When highlighting transportation in the EU-28, freight transportation activities are estimated to amount to 3516 billion tonne-kilometers (tkm) in 2015 (EU, 2017); this figure includes intra-EU air and sea transportation but not transportation activities between the EU and the rest of the world. A tkm is defined as the product of the transported mass in tonnes times the distance covered in kilometers (km). The EU (2017) states that in 2015 road transportation accounted for 49% of this total, rail for 11.9%, inland waterways for 4.2%, and oil pipelines for 3.3%; intra-EU maritime transportation was the second most important mode with a share of 31.6% while intra-EU air transportation only accounted for 0.1% of the total. Between 1995 and 2015, the growth rate of freight transportation in the EU-28 on each mode was positive, road transportation increased by another 33.7%, which represents an average annual growth of 1.5% (EU, 2017) and the highest growth rate of all modes, when intra-EU air transportation is not taken into account. The total growth rate of freight transportation within that period was 23.6% (EU, 2017). Having a look at the modal split of freight transportation in the EU-28, one can observe that the portion of road transportation increased from 45.3% in 1995 to 49% in 2015 (EU, 2017); the portion of all other transportation modes, except for intra-EU air transportation, decreased slightly during the same period. In the USA, freight transportation activities were estimated to be 8301.5 billion tkm in 2014; road transportation accounted for 45.9% of this total (EU, 2017). Overall, there was an increase of 17.6% of freight transportation activities in the USA between 1995 and 2014 (EU, 2017).
Total passenger transportation activities in the EU-28 by any motorized means of transportation are estimated to amount to 6602 billion passenger-kilometers (pkm) or on average around 12.962 km per person in 2015 (EU, 2017); this figure includes intra-EU air and sea transportation but not transportation activities between the EU and the rest of the world. A pkm is defined as the product of transported passengers times the distance covered in km. EU (2017) states that passenger cars accounted for 71.5% of the total pkm in 2015, powered two-wheelers for 1.9%, buses and coaches for 8.2%, railways for 6.7% and tram as well as metro for 1.6%; intra-EU air and intra-EU maritime transportation contributed 9.8% and 0.3%, respectively. Between 1995 and 2015, the growth rate of passenger transportation activities in the EU-28 on each mode was positive except for intra-EU maritime transportation (ā29.7%); passenger cars increased by 20.9%, powered two-wheelers by 11.1%, buses and coaches by 5.6%, railway by 26.1%, tram and metro by 38.9%, and air by 86.5%. The total growth rate of passenger transportation within that period was 23.8% (EU, 2017). Having a look at the modal split of passenger transportation in the EU-28, one can observe that the portion of air transportation increased from 6.5% in 1995% to 9.8% in 2015; during the same period, the portion of motorized individual transportation modes as well as bus and coach decreased slightly, the portion of intra-EU maritime transportation was halved, and the portion of public transportation modes rose slightly (EU, 2017). In the USA, passenger transportation activities were estimated at 7845.1 billion pkm in 2015; passenger cars, including light-duty vehicles, accounted for 27.3% of this total (EU, 2017). Overall, there was an increase of 18.3% of passenger transportation activities in the USA between 1995 and 2015 (EU, 2017).
In the EU, 26,134 persons were killed in road accidents (fatalities within 30 days) in 2015, which is 0.7% more than in 2014 (EU, 2017). Nevertheless, the number of fatalities was reduced by 66.2% between 1990 and 2015 (EU, 2017). In rail transportation, 27 persons lost their lives in 2015; this figure does not include casualties among railway employees or other people run over by trains (EU, 2017). Air transportation accounted for 150 fatalities in 2015 (EU, 2017). In 2015, the total GHG emissions in the EU-28 were 4451.8 million tonnes CO2 equivalents (CO2e), the transportation sector accounted for 1182.9 million tonnes CO2e, which is 26.6% (EU, 2017). The total GHG emissions were reduced by 22.1% between 1990 and 2015, whereas the transportation-related GHG emissions increased by 23% during the same period (EU, 2017). In 2015, road transportation acc...