Occupancy and GHG emissions: thresholds for disruptive transportation modes and emerging technologies

This paper estimates the environmental impact of alternative and conventional transportation technologies across the dimensions of service mode and power source pathway. We simulate the Well-to-Wheel energy consumption and GHG emissions of eight transit buses and passenger car powertrains. Vehicles are simulated under three generalized North American operating contexts (450 operating scenarios) using Autonomie and the GREETdatabase. All technologies are normalized by passenger-service-mode-trip-km-travelled GHG emissions to facilitate equivalent comparison. The results indicate that all simulated mobility solutions carry a large variability; however, the most environmentally competitive solutions are fuel cell electric car-share, battery electric car-share, and battery-electric bus, all powered by low-carbon intensity power sources at average occupancy (0.23–19.7 g CO2e passenger-service-mode-trip-km-travelled-1). Furthermore, transit bus technologies have the potential to reduce up to 2.3 times more GHG per passenger-trip than comparable ride-share technologies. Overall, this paper defines occupancy GHG emission thresholds formobility solutionsto inform environmental decision-making processes.