Many jurisdictions are focused on achieving very low or net-zero greenhouse gas (GHG) emissions by mid-century, bringing a spotlight to the biggest challenges in decarbonisation.

The transportation sector is responsible for about one-quarter of global GHG emissions and emissions are growing, even in the developed world where other emissions are generally flat. Liquid fuels made from oil dominate the sector; they are easy to transport and store, contain a great deal of energy for their weight and volume, and enable use of internal combustion engines. The degree of difficulty in decarbonising transport varies across the sector. Electrification is relatively easy for smaller vehicles that travel shorter distances carrying lighter loads. For these vehicles, the added weight of a battery is less of a hindrance and the inherently simpler and more efficient electric motor and drivetrain (the system that delivers power from the motor to the wheels) make up for some of the weight penalty. However, the heavier forms of transportation are among the fastest growing, meaning that we must consider solutions for these more difficult vehicles as well.

The challenge of decarbonising these sectors and the technologies to overcome these challenges are global, but this paper focuses on policy options in the United States.