Exploring the potential of a novel passenger transport model to study the decarbonization of the transport sector

To explore sustainability strategies in the transport sector in a holistic way, a model dedicated to passenger transportation has been created as a part of the multiregional WILIAM model (Within Limits Integrated Assessment Model). Based on system dynamics, our model increases the diversity of existing passenger transport models within Integrated Assessments Models by offering a detailed representation of the dynamics of the transition for different technologies and transport modes combining technological and behavioural changes. It calculates the energy demand, direct emissions and additional material requirements of the transport sector and can be linked to other submodules of WILIAM to study different feedback loops. Here we report the validation of the offline model and illustrate its usefulness and practical applicability. First, a Baseline transport scenario for Spain was developed and parametrized. This scenario describes the plausible evolution of the Spanish passenger transport system in the absence of ambitious environmental policies but nevertheless achieves a reduction of total direct CO2 emissions from passenger transport from 66 Mt CO2/year in 2022 to 60 Mt CO2/year in 2035, after which emissions remain constant until 2050. Subsequently, following the Avoid-Shift-Improve approach, various behavioural change measures and technological improvements were introduced. The comparison of the different modelled measures reveals that the most effective tested strategy to reduce direct emissions is the transition to battery electric power trains for cars, buses, and motorcycles, however at the cost of the highest material requirements. Further work will be dedicated to the study of the implications of the link of this submodule with the rest of WILIAM.