Transportation is a critical pillar of modern society. Over the past decades, growth in mobility of people and goods have been both enabled by and dependent upon fossil fuels. Strong action is needed to break this dependence in order to reduce CO₂. The overall aim of this thesis is to support the transition towards climate neutral transportation in Sweden considering local, regional, and national settings, by use of TIMES-based ESOMs. This is addressed by i) developing and adapting transport sector representation in TIMES models considering context specific conditions and preferences, ii) applying the models to define and explore alternative long-term scenarios that meet the overall goals, iii) and identify key measures and policy implications for achieving climate neutral transportation.

In Paper I (Local setting) key considerations and requirements in respect of modelling local energy transition of transportation in a TIMES energy system modelling framework was outlined. The model was then applied to address potential trade-offs between global climate concerns and local air quality issues (Paper II – Local setting). The results showed that decarbonisation with biofuels does little to enhance local air quality, while zero-emission vehicles – that eliminate all local tailpipe emissions – can induce significant upstream CO₂ emissions (from energy supply sectors). Comprehensive multi-level strategies are needed to drastically reduce both CO₂ and local air pollutants. In Paper III (Regional setting), a participatory modelling approach was applied that involved local practitioners from 15 municipalities. The model results showed that strong national policies can drive down CO₂ emissions drastically, and that the impacts from sub-national strategies was very limited under these policies. Still, during the discussions with local practitioners it was emphasized that local action is needed for enabling the measures seen as cost-efficient in the model analysis.

The TIMES-Sweden model was adapted and used to explore key decarbonisation options in passenger and freight transportation, in a whole-energy-systems perspective. The model was disaggregated to capture underlying contextual heterogeneity in passenger transportation found across the country (Paper IV – National setting). The results showed that different policy strategies have different implications depending on the context, thus, underpinning a shift from one-size-fits-all policies into more regionally tailored strategies. Next (Paper V – National setting), the same model was used to investigate principally different modes of decarbonising domestic freight transportation. The results showed that road freight electrification reduces total demand for electricity over the entire energy system compared to the biofuel and the e-fuel pathways respectively, while also freeing biomass for other purposes than producing biofuels for road vehicles.

Finally, the usefulness of ESOMs to identify policies to accelerate the decarbonization of transportation has been demonstrated, while outlining some challenges. For local level, the necessary data to calibrate the model was often not available, or available but with a system boundary representation incompliant with the model approach (e.g., fuel statistics). At the national level, a new approach was introduced that capture the underlying contextual factors of different actors. While capturing differences between urban, suburban and rural conditions, more research is needed to identify policies that ensure a just transition across socioeconomic groups.