We evaluate the N-shaped environmental Kuznets curve (EKC) using panel quantile regression analysis. We investigate the relationship between CO2 emissions and GDP per capita for 74 countries over the period of 1994–2012. We include additional explanatory variables, such as renewable energy consumption, technological development, trade, and institutional quality. We find evidence for the N-shaped EKC in all income groups, except for the upper-middle-income countries. Heterogeneous characteristics are, however, observed over the N-shaped EKC. Finally, we find a negative relationship between renewable energy consumption and CO2 emissions, which highlights the importance of promoting greener energy in order to combat global warming.

This study has developed and applied a framework to analyse barriers, opportunities, and potential solutions for the diffusion of alternative fuels, here exemplified by liquefied biogas (LBG) for heavy trucks. The study is based on expert and stakeholder interviews in Sweden. Also, the study estimates a cost example of using heavy duty LBG-trucks instead of conventional diesel trucks. The framework is based on two previously published frameworks to categorise barriers, opportunities, and potential solutions and comprises five categories: financial, technical/commercial/physical, policy, public acceptability, and market structure/interaction barriers. Each category considers both the system and actor levels. The results of this study fit the framework's categories well, and the framework is appropriate for analysing the diffusion of liquefied biogas for heavy trucks, and other technologies with similar characteristics. The results further indicate that a network level, in addition to the system and actor levels, could advance our understanding of renewable energy diffusion. The most mentioned opportunities were climate/environmental benefits, potential profitability, and newly introduced policies. The cost estimates show that given current taxes and policies in Sweden, the costs of using LBG-trucks are only marginally higher than those of using conventional diesel trucks. Commonly cited barriers were financial issues, an unstable policy context, lack of infrastructure, and lack of knowledge. Suggested solutions for overcoming barriers were financial incentives, a stable policy context, demonstration projects, and information campaigns. Improved knowledge and working together throughout the biogas value chain, with a palette of renewable energy options, are important for accelerating a sustainable renewable fuel diffusion. Several policy instruments that currently exists in Sweden already target the mentioned barriers. Thus, it is important to continuously evaluate policy instruments to understand if they are effective and efficient, or if anything need to be changed to reach the targets of the policy instrument. © 2021 The Authors

This paper presents a review of past and present public policy instruments in Europe promoting a modal shift of freight transports. The identified policy instruments are categorized based on several shared characteristics. To the extent that ex-post evaluations are available, policy performance is discussed, and the evaluations are compared.

The study identifies 93 public policy instruments in Europe. The most common type of policy is subsidies/grants to rail and/or water implemented at the national level. Most policy instruments only focus on the promotion of one specific transport mode, which most commonly is rail.

Evaluations of policy performance were found for 20 policy instruments. The evaluated policy instruments are mainly subsidies/grants at the national level, or policy instruments at EU level. The bias in evaluation towards these types of policy instruments is partly explained by the commitment to evaluation at EU level, and the need for permission by the European Commission to implement and prolong subsidies/grants classified as state aid. The evaluations differ in methodology and regarding what type of performance indicators that are evaluated. The evaluation guidelines and criteria that exist at EU level are often followed to some extent but interpreted differently depending on for example type of policy and data availability. Thus, comparing policy performance is difficult.

In general, there seem to be a more positive performance of policy instruments promoting a modal shift to rail than to waterborne transports. Several evaluations of EU-policy instruments describe a poor or a mixed performance of the policy instruments, while the performance of subsidies/grant at national level are often considered positive by the evaluations. A commonly mentioned factor for underachievement of the policy instruments is problems related to outreach of the policy, lack of applications, long and complicated application processes and a high administrative burden for the companies applying for financial support. Targets for the policy instruments are often broad and general, with a lack of clarity, making it difficult to meet all objectives, as well as to evaluate the policy instruments effectiveness and efficiency. Thus, well-defined targets, as well as better outreach and simpler processes could be one way forward in improving modal shift policy instruments in Europe.