Pacific Southwest Region 9 UTC

Life Cycle Assessment of Environmental and Economic Impacts of Deploying Alternative Urban Bus Powertrain Technologies in the South Coast Air Basin

Project Number


Project Summary

The objective of this project is to perform a life cycle characterization of greenhouse gas emissions, criteria pollutant emissions, water footprints, and costs of conventional and alternative urban bus powertrains. The findings of this project will inform transit agencies and government agencies in developing transition pathways for urban bus fleets to cost-effectively meet environmental objectives in California. Life cycle includes the stages of material extraction, material transport, manufacturing, use, and end-of-life.


Many municipalities and state governments have set targets for one or more of the following objectives: greenhouse gas reduction, compliance with air quality standards, and increasing renewable utilization. Changes in the transportation sector are a key part of these efforts due to the large contribution of this sector to greenhouse gas & criteria air pollutant emissions, as well as overall energy usage. While a large amount of attention has been focused on shifts in the light-duty transportation subsector by means of improving efficiency and proliferation of electric vehicle powertrains, the heavy duty sector is also in need of emissions reduction strategies. Heavy-duty vehicles such as buses are not only a large contributor to criteria pollutant emissions, but are also sources of emissions that are embedded within population centers, contributing to degraded urban air quality. This is especially important in California, and particularly in the South Coast Air Basin of the state where local geography combined with high populations give rise to significant air quality issues and difficulty in meeting federal ambient air quality standards. Policy efforts to address this with respect to buses are codified in regulations such as the California Air Resources Board Innovative Clean Transit measure, with the goal of transforming the statewide transit bus fleet by 2040 through phasing-in zero emission bus purchases.


Multiple options exist for transitioning the urban bus fleet technology portfolio to contribute to emissions reduction goals. These include but are not limited to: 1) fuel-switching to lower-carbon, cleaner burning fuels such as natural gas, 2) deployment of all-electric battery electric buses – both short-range with roadway recharging and long-range with large battery sizes, and 3) deployment of hydrogen fuel cell buses. However, each of these options vary in their overall effectiveness in reducing different emission types over their life cycle, associated life cycle costs, ability to meet operational needs of transit agencies, and life cycle environmental footprint. In order for transit agencies to determine the cost- and environmentally-favorable pathways for transitioning urban bus fleets to reduce emissions, information regarding the life cycle greenhouse gas and criteria pollutant emissions, costs, and environmental externalities such as water resource impacts for potential urban bus technologies must be provided.


This project therefore aims to provide this insight using the following phases. The first phase will focus on acquiring life cycle inventory data for different urban bus powertrain technologies by utilizing available life cycle databases and literature studies. The second phase includes modeling of urban bus fleet operation to accurately capture operating energy needs and associated emissions in the context of powertrain characteristics and bus scheduling needs. The third phase will focus on utilizing the Brightway2 LCA framework in combination with the development of economic modeling methodologies for alternative bus powertrain deployment for performing full life cycle assessment of different urban bus powertrain options to determine per-mile greenhouse gas emission, criteria pollutant emission, cost, and environmental footprint performance. The intended outcome of this project is to provide data on the life cycle performance of different powertrain options on multiple criteria for use by state agencies and transit agencies in more effectively planning the transition of urban bus fleets to meet environmental objectives.


Project Status

In progress



Topic Area

Urban Mobility

P.I. Name & Address

Professor, Mechanical and Aerospace Engineering
University of California Irvine

Funding Source: UC ITS Mobility Research Program (SB1)

Funding Amount: $57,840.00

Start and End Dates: January 1, 2018 to June 30, 2020