Harnessing hybrid buses in the near term leads to faster transit decarbonization.

To achieve net-zero emissions, transit systems will eventually have to transition to fully electric buses. We introduce an integrated decision-making and energy modeling framework to analyze transition strategies from diesel to zero-emitting buses under various budget scenarios. Using a detailed energy model of the buses to predict fuel usage, we then optimally assign types of buses to scheduled trips to minimize diesel consumption and emissions. Applying this framework to the Pioneer Valley Transit Authority network, we find that under realistic budget and infrastructure constraints, an electrification future that allows a mix of electric and hybrid buses reduces emissions more effectively than an all-electric future. Specifically, for a fixed budget, incorporating hybrid buses results in an additional 6% emissions reduction over the 18-year planning horizon compared to an electric-only future. This shows that hybrid buses can speed up the elimination of diesel buses and maximize emissions reduction while mitigating infrastructure and financial constraints. Our framework evaluates different fleet transition futures and provides transit agencies with a data-driven framework to plan investments and meet their decarbonization targets under realistic budgetary and infrastructure constraints.