The European Union aims at net-zero emissions by 2050. A key sector to achieve this goal is road transport, where emissions show no signs of reducing but continue to grow. A review of policies undertaken by EU member states and the G20 to reduce transport emissions reveals that both present and planned policies focus on binding supply-side measures, but offer only weak demand-side incentives. To address this imbalance, we developed a downstream, demand-side policy prototype through an expert interview design process. We call the prototype “cap-and-surrender” because it caps road emissions, and then allocates tradable emission allowances to individual vehicles that drivers surrender at each fill-up. Allowance pricing, both by the state and in the secondary market, is designed to incentivize decarbonization of the sector. Though the system would require significant investment, its revenue potential to the state should exceed this investment by several multiples. We discuss the potential economic, environmental and social impacts of the policy, as assessed by European transport experts. We find that the approach can deliver significant transport emission reductions in an effective and economically efficient manner. Through the appropriate design of national allocation rules and a gradual phasing in of cap and surrender, potential negative social consequences can be mitigated, and public acceptance of the policy promoted.