Transportation infrastructures in a low carbon world: An evaluation of investment needs and their determinants

Transportation infrastructures will either lock in transportation patterns in high CO₂ modes or foster low-carbon pathways. At the same time, increases in future mobility demand require the rapid development of new infrastructures. Here we quantify investment needs for transportation infrastructures over time to achieve both development and climate objectives. We compared investment needs between world regions and analyzed their main determinants. To do so, we built socioeconomic scenarios with the Imaclim-R integrated assessment model, combining alternatives for model parameters that determine mobility patterns. We then estimated the levels of investment that are consistent with the passenger and freight transportation trends in the different scenarios with and without climate policy. Finally, we used a global sensitivity analysis to identify the determinants of investments in low-carbon scenarios. We find that the expenditure needed for transportation infrastructure is lower in low-carbon pathways than in baseline scenarios. This result holds true at both the global and regional scales and is robust to the uncertainties considered. This overall decrease is brought about in particular by a reduction in transport activity. Rail utilization rates and road construction costs are determining factors for investment in all regions. Modal shift from road to rail can be a lever to reduce investment needs only if combined with action on rail infrastructure occupancy. To obtain a comprehensive assessment of the costs related to the transport sector in a low-carbon world, additional investments not considered in this study related to energy efficiency or alternative fuels use should be integrated.