Transport and fossil fuels have been intrinsically linked since the Industrial Revolution, from which time all transport modes (road, rail, waterborne, aviation) have come to rely on fossil fuel-based technologies. Transport's apparent addiction to oil in particular has become more problematic as climate change has moved ever higher up the political agenda. Historically, the EU has attempted to address the negative environmental externalities from transport by adopting different policy instruments on a mode-by-mode basis (van Lier and Macharis 2015: 120-121). Despite this, however, the EU has not been able to break the link between transport growth and emissions growth: between 1995 and 2018, overall passenger transport has grown by 30 per cent and freight by 40 per cent (European Commission 2020: 23), contributing to a rise in road traffic emissions from 620 to 786 million tonnes CO2 equivalent since 1990 (ibid). Transport's share of total greenhouse gas (GHG) emissions in the EU27 has increased, from 16.5 per cent in 1990 to 27.2 per cent in 2018, due to a combination of reductions in other sectors and the growth in transport volumes (European Commission 2020: 137). Thus, transport represents an acute climate challenge, and it is vital for the EU to act urgently if it is to meet its long-term goal of a 90 per cent reduction in transport emissions by 2050 (European Commission 2020b: 2). Achieving this reduction requires political support in particular for the replacement of fossil fuel technologies with batteries or alternative fuels. Some transport modes, like roads and railways, are further along in their technological development, compared to aviation and maritime which are only just starting their energy transitions. Thus, different transport modes face different challenges.Until the Commission's launching of its European Green Deal (EGD) in 2019, EU climate mitigation legislation covering transport relied largely on regulatory measures such as standards for fuel efficiency and vehicle emissions, or instruments to incentivize investment in alternative fuels, for example promoting renewable energy and biofuels. With the launch of the EGD and associated 'Fit for 55' package (European Commission 2021a), a turn towards more market-based instruments, including efforts to extend the scope of the EU emission trading system (ETS), became evident, alongside efforts to tighten existing emission standards.Historically, EU legislators have often been forced to water down policy proposals relating to environmental protection in transport, in the face of lobbying from structurally powerful incumbent industry actors, particularly large car manufacturers that often have close relationships with their national (Member State) governments (Dionigi 2017; Skete 2017). There have also been potentially effective policy instruments that have been neglected, or blocked, due to a lack of competence at EU level, especially regarding fiscal instruments which remain the responsibility of Member State governments, or which have been sty...