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

ABSTRACT

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 decarbonize 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, organizational 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 standardized 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.

KEYWORDS:

• passenger transport
• decarbonization
• policy
• scenarios
• pathways

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 60% of which is linked to passenger transportation (FIT, 2019).

2 For instance Edelenbosch et al. (2017) decompose mitigation in transport scenarios through the standard four indicators inspired by the ASI framework: population, activity per capita, modal shares, energy intensity per mode and fuel mix.

3 More generally, demand-side aspects of mitigation have been insufficiently addressed in all sectors so far with energy models and remain a key research challenge (Creutzig et al., 2018).

4 (Briand et al., 2017; Kainuma et al., 2017; Pye & Li, 2017; Tovilla & Buira, 2017) (https://www.iddri.org/en/project/deep-decarbonization-pathways-mobility).

5 The full dashboards and standardized graphs for the eight DDPs can be found in the Supplementary material.

6 Despite aircraft efficiency gains and increasing biofuel use, such measures are only sufficient to keep emissions at current levels due to rapid sectoral growth. Policies focused on demand-side reductions are therefore crucial for this sector.

7 Log-Mean Divisia Index.

8 For instance, mobility projection in the TEC scenario for the UK is aligned with the forecasts produced by the UK Department for Transport (DfT. Road traffic forecasts 2015).

9 As opposed to ageing, for instance, which is seen as another important driver of the reduction of average mobility demand but is not actionable and will not work in all scenarios.

10 Urban planning towards ‘compactification’ is seen as a key strategy to reduce transport emissions (Creutzig, 2016).

11 This reflects one of the visions debated in France in recent years, which could be challenged in the context of more constrained bioenergy resources and the faster improvement of EV batteries.

Additional information

Funding

This work was supported by the Agence Nationale de la Recherche of the French government through the Investissements d’avenir [ANR-10-LABX-14-01] programme.