A pathway design framework for sectoral deep decarbonization: the case of passenger transportation

International audience; The transport sector represents 25% of global CO2 emissions, and large-scale emission reductions are needed in this sector to meet the objectives of the Paris Agreement. Long term low-greenhouse gas emissions development strategies are key enabling instruments to reconcile near-to-medium term action with long term objectives. While a range of options exist to decarbonise the passenger transport sector, the detailed sequencing of actions and resulting transformations over time remain largely unexplained in policy debates. Scenarios from transport-energy modelling provide useful insights about technological strategies but often overlook other key drivers of transportation futures, including social, organisational and spatial determinants of mobility, and are not easily usable to inform policy discussions. In this paper, we introduce a new framework to design and compare long term national decarbonization pathways for passenger transportation. This framework is based on an iterative method combining detailed qualitative storylines, full scenario quantification and standardised dashboard reporting, adapted from the general Deep Decarbonization Pathways (DDP) framework. For illustration, the method is applied by four national research teams in Japan, the UK, Mexico and France, to derive country-specific decarbonization pathways. The results across countries show that: i) strong action is needed across all types of options to reach deep decarbonization, notably demand-side solutions; ii) deep decarbonization is compatible with other policy priorities such as satisfying mobility needs at affordable costs; and iii) strategies should be tailored to mobility purpose, local contexts and national circumstances. The framework can be adapted to other sectors and should be further developed in the context of future policy processes. Key Policy insights-Understanding deep decarbonization of the passenger transport sector requires a novel conceptual approach that articulates metrics across diverse dimensions (social, economic, energy, etc.) to increase policy relevance.-We introduce a framework to design national decarbonization pathways for passenger transportation following this approach.-Strong action across all pillars of decarbonization including demand-side solutions is needed to reach deep emissions reductions.-Deep decarbonization is compatible with other policy priorities such as satisfying mobility needs at affordable costs.-Strategies should be tailored to mobility purposes, local contexts and national circumstances.