Life Cycle Environmental Impact of Houston METRO System – Evaluation of Electric Alternatives

Urban mass transit systems alleviate road traffic congestion and reduce the total greenhouse gas emissions (GHGs) from the transportation sector. Houston METRO operates buses along 86 routes in the Greater Houston area, and three light-rail lines (red, purple and green lines) that have a average daily ridership of 61,000 passengers. Public transportation systems reduce the total emissions of criteria air pollutants (CAPs) from urban centers, and form an integral part of environmental strategies to combat climate change. A comprehensive energy and environmental life cycle assessment (LCA) study is vital to quantify the improvements, and identify any potential systemic modifications that could further lower environmental impacts. As per EPA’s 2014 National Emission Inventory, mobile sources (on- and off-road vehicles) contributed the highest share (67%) of nitrogen oxide emissions, and second-highest share (23%) of volatile organic (VOC) emissions in the Greater Houston Area. This region has historically been affected by severe summer ozone episodes that impact public health and welfare. The METRO system is a key element in Houston’s infrastructure that can be expanded to lower emissions of CAPs and GHGs, and improve regional air quality. Any expansion of the METRO system includes upfront infrastructure, and supply chain processes, which will have an environmental impact. Currently, there is a lack of comparative studies for relative emissions and environmental impacts between passenger automobiles and METRO routes in Houston. This project will address this critical gap and develop environmental life cycle assessments for the bus and light-rail routes operated by METRO. This project will also provide quantitative estimates for GHG and CAP emissions, when considering future route expansions, and fleet modification to electrical vehicles. A novel component of the project is the development of a decision making that would provide CO2 and energy payback times as a function of ridership and mode shifts from automobile to METRO bus/light-rail. Results from this project will serve as a guidance framework in order to evaluate the effects of the decision to expand METRO system, and estimate the contribution of METRO system in realizing the environmental objectives of the Greater Houston Area.


  • English


  • Status: Completed
  • Funding: $46500
  • Contract Numbers:


  • Sponsor Organizations:

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Managing Organizations:

    Transportation Consortium of South-Central States (Tran-SET)

    Louisiana State University
    Baton Rouge, LA  United States  70803
  • Project Managers:

    Melson, Christopher

  • Performing Organizations:

    Prairie View A&M University

    Department of Civil & Environmental Engineering
    P.O. Box 519
    Prairie View, TX  United States  77446
  • Principal Investigators:

    Kommalapati, Raghava

    Du, Hongbo

    Choe, Doeun

  • Start Date: 20190815
  • Expected Completion Date: 20210215
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers Program

Subject/Index Terms

Filing Info

  • Accession Number: 01713220
  • Record Type: Research project
  • Source Agency: Transportation Consortium of South-Central States (Tran-SET)
  • Contract Numbers: 69A3551747106
  • Files: UTC, RIP
  • Created Date: Aug 5 2019 7:50PM