Bus and Rail Network Design and Exposure to Extreme Heat

We have developed a framework for assessing exposure to environmental conditions (e.g., extreme heat, precipitation, or cold) based on network analyses of parcels, transit networks, and transit schedules. We simulate for every residential parcel in a city how long they are exposed based on their walking times to and from transit and their waiting times at transit. Our results show that, in the case of Southwest U.S. cities, that when temperature is highest (midday), exposure is greatest due to lower headways at offpeak times. We overlay social vulnerability indices to show which neighborhoods are at greatest risk. With this information we are able to direct transit agencies towards strategic investments in schedule changes, public outreach, and communication of transit schedules to reduce these vulnerabilities.

Embodied Emissions in Rail Infrastructure: A Critical Literature Review

Environmental Research Letters, 14(12), doi: 10.1088/1748-9326/ab442f

This paper investigates the state of knowledge in quantifying the embodied greenhouse gas (GHG) emissions in rail infrastructure and develops a sketch model for estimating the GHG impact of rail infrastructure based on the literature. A literature review identified 22 publications, containing 57 case studies, at least touching on the embodied GHG for different types of rail infrastructure. The cases studies include high speed rail, intercity rail, light rail, commuter rail, heavy rail, freight, and metro rail. The paper examines the GHG impact per kilometre of rail infrastructure reported across the case studies and compares the boundaries, functional units, methods, and data used. Most studies employed process-based LCA for an attributional analysis. The embodied emissions associated with the case studies range from 0.5 to 12 700 tCO2 km−1; much of the variation is dependent on the proportion of the rail line at-grade, elevated, or in a tunnel. However, large ranges in GHG per kilometre remain after controlling for elevated and tunneled distance. Comparing the embodied emissions across the rail types was challenging, due to the large variations in system boundaries, study goals, and inventory methods adopted in the publications. This review highlights the need for standardization across the reporting of embodied GHG for rail infrastructure to better facilitate hot spot detection, engineering design and GHG policy decision making. The statistical model finds that overall ~941(±168) tCO2e are embodied per kilometre of rail at-grade, and tunneling has 27 (±5) times more embodied GHG per kilometre than at-grade construction. The statistical model is based on the findings of published literature and does not explicitly consider function, geometry, specifications, emphasis on whole lifecycle, legislative constraints, socio-economic factors, or the physical and environmental conditions of the construction site.

Greenhouse Gas and Air Quality Effects of Auto First-Last Mile Use With Transit

Transportation Research Part D, 2017, 53, pp. 306-320, doi: 10.1016/j.trd.2017.04.030

With potential for automobiles to cause increased greenhouse gas emissions and air pollution relative to other modes, there is concern that using automobiles to access or egress public transportation may significantly increase the environmental impacts from door-to-door transit trips. Yet little rigorous work has been developed that quantitatively assesses the effects of transit access or egress by automobiles. This research evaluates the life-cycle impacts of first-and-last mile trips on multimodal transit. An environmental life-cycle assessment of transit and automobile travel in the greater Los Angeles region is developed to evaluate the impacts of multimodal transit trips by utilizing existing transportation life-cycle assessment methods. First-last mile automobile trips with transit may increase multimodal trip emissions significantly, mitigating potential impact reductions from transit usage. In some cases, multimodal transit trips with first-last mile automobile use may have higher emissions than competing automobile trips. In the near-term, first-last mile automobile trips in some Los Angeles transit services may account for up to 66% of multimodal greenhouse gas trip emissions, and as much as 75% of multimodal air quality impacts. Fossil fuel energy generation and combustion, low vehicle occupancies, and longer trip distances contribute most to increased multimodal impacts. Supply chain analysis indicates that life-cycle air quality impacts may occur largely locally (in Los Angeles) or largely remotely depending on the propulsion method and location of upstream life-cycle processes. Reducing 10% of transit system greenhouse emissions requires a shift of 23–50% of automobile first-last mile trips to a neutral emissions mode.

Heat Exposure and Transit Use: Travel Behavior and Infrastructure

ASU Report No. ASU-SSEBE-CESEM-2017-CPR-001

Public transit necessitates environmental exposure and there is increasing recognition that in a future with hotter temperatures new strategies are needed to protect passengers. Arizona State University’s Spring 2017 Urban Infrastructure Anatomy course assessed travel behavior, public transit stop design, and heat exposure to develop recommendations for mitigating heat exposure. Travel surveys, analysis of infrastructure characteristics, and thermal imaging were used to assess exposure. A suite of mitigation strategies was developed from a literature review, conversations with experts, and review of other transit systems. Focusing on neighborhoods in Tempe, Arizona, strategies are developed for protecting future riders from negative health outcomes.

The Net Greenhouse Gas Impact of the Sheppard Subway Line

Transportation Research Part D: Transport and Environment, 2017, 51, 261-275, doi: 10.1016/j.trd.2017.01.007

As cities work to reduce their total greenhouse gas (GHG) emissions, the transportation sector is lagging, accounting for a growing percentage of total emissions in many cities. The provision of public transit, and specifically urban rail transit, is widely seen as a useful tool for reducing urban transportation GHG emissions. There is, however, limited understanding of the net impact of new metro rail infrastructure on urban emissions. This paper examines the net GHG emission of the Sheppard Subway Line in Toronto, Canada. The GHG emissions associated with construction, operation, ridership and changes in residential density associated with the provision of the new metro rail infrastructure are assessed. These components are then combined and compared to calculate the net GHG impact across the study period, which extends from opening in 2002 through 2011. The GHG payback period is calculated. After nine years of operation, the Sheppard Subway Line is found to have nearly paid back its initial GHG investment in the optimistic case. The payback was due to the calculated mode shift from automobiles, changes in residential density and associated energy savings in the station pedestrian catchment areas. The payback period is very sensitive to the potential for induced demand to backfill the mode shifted automobile kilometres.

Transit System Design and Vulnerability of Riders to Heat

Journal of Transportation and Health, 2017, 4, pp. 216-225, doi: 10.1016/j.jth.2016.07.005

In the United States public transit utilization has increased significantly in the last decade and is considered a critical component in reducing energy use and greenhouse gas emissions in urban areas. Despite public transit׳s climate change mitigation potential, the use of transit necessitates environmental exposure which may be a health hazard during periods of extreme heat. Transit system design, which includes stop location and schedules, is shown to contribute to environmental exposure resulting from access and waiting. Using Los Angeles Metro (Los Angeles County, CA) and Valley Metro (Maricopa County, AZ) as case studies of systems operating in extreme heat conditions, the research demonstrates how system design contributes to heat exposure times that vary significantly between neighborhoods. Household level access (walking) time estimates are developed using a shortest path algorithm to nearby transit stops. Waiting time estimates for individual transit stops are derived from published transit schedules and on-board survey responses. The results show that transit users from areas with low residential density, limited high capacity roadways and irregular street networks, and not located along direct paths between major activity centers are likely to experience prolonged access and/or waiting times. Public transit may help mitigate climate change impacts but transit proponents, agencies and planners should be cognizant of the impact an uncertain climate future may have on a growing base of transit riders. These insights can allow us to proactively govern and adapt transit systems to protect people from a growing health concern.

Time-based Life-cycle Assessment for Environmental Policymaking: Greenhouse Gas Reduction Goals and Public Transit

Transportation Research Part D, 2016, 43, pp. 49-58, doi: 10.1016/j.trd.2015.12.003

As decision-makers increasingly embrace life-cycle assessment (LCA) and target transportation services for regional environmental goals, it becomes imperative that outcomes from changes to transportation infrastructure systems are accurately estimated. Greenhouse gas (GHG) reduction policies have created interest in better understanding how public transit systems reduce emissions. Yet the use of average emission factors (e.g., grams CO2e per distance traveled) persists as the state-of-the-art masking the variations in emissions across time, and confounding the ability to accurately estimate the environmental effects from changes to transit infrastructure and travel behavior. An LCA is developed of the Expo light rail line and a competing car trip (in Los Angeles, California) that includes vehicle, infrastructure, and energy production processes, in addition to propulsion. When results are normalized per passenger kilometer traveled (PKT), life-cycle processes increase energy use and GHG emissions up to 83%, and up to 690% for smog and respiratory impact potentials. However, the use of a time-independent PKT normalization obfuscates a decision-maker’s ability to understand whether the deployment of a transit system reduces emissions below a future year policy target (e.g., 80% of 1990 emissions by 2050). The year-by-year marginal effects of the decision to deploy the Expo line are developed including reductions in automobile travel. The time-based marginal results provide clearer explanations for how environmental effects in a region change and the critical life-cycle processes that should be targeted to achieve policy targets. It shows when environmental impacts payback and how much reduction is achieved by a policy-specified future year.

Cost-effectiveness of Reductions in Greenhouse Gas Emissions from High-speed Rail and Urban Transportation Projects in California

Transportation Research Part D, 2015, 40, pp. 104-113, doi: 10.1016/j.trd.2015.08.008

As California establishes its greenhouse gas emissions cap-and-trade program and considers options for using the new revenues produced under the program, the public and decision-makers have access to tenuous information on the relative cost-effectiveness of passenger transportation investment options. Towards closing this knowledge gap, the cost-effectiveness of greenhouse gas reductions forecast from High-Speed Rail are compared with those estimated from recent urban transportation projects (specifically light rail, bus rapid transit, and a bicycling/pedestrian pathway) in California. Life-cycle greenhouse gas emissions are joined with full cost accounting to better understand the benefits of cap-and-trade investments. Results are largely dependent on the economic cost allocation method used. Considering only public subsidy for capital, none of the projects appear to be a cost-effective means to reduce greenhouse gas emissions (i.e., relative to the current price of greenhouse gas emissions in California’s cap-and-trade program at $11.50 per tonne). However, after adjusting for the change in private costs users incur when switching from the counterfactual mode (automobile or aircraft) to the mode enabled by the project, all investments appear to reduce greenhouse gas emissions at a net savings to the public. Policy and decision-makers who consider only the capital cost of new transportation projects can be expected to incorrectly assess alternatives and indirect benefits (i.e., how travelers adapt to the new mass transit alternative) should be included in decision-making processes.

Policymaking Should Consider the Time-dependent Greenhouse Gas Benefits of Transit-oriented Smart Growth

Transportation Research Record, 2015, 2502, pp. 53-61, doi: 10.3141/2502-07

Cities are developing greenhouse gas (GHG) mitigation plans and reduction targets on the basis of a growing body of knowledge about climate change risks, and changes to passenger transportation are often at the center of these efforts. Yet little information exists for characterizing how quickly or slowly GHG emissions reductions will accrue given changes in urban form around transit and whether benefits will accrue quickly enough to meet policy year targets (such as reaching 20% of 1990 GHG emissions levels by 2050). Achieving GHG reductions through integrated transportation and land use planning is even more complicated for cities because changes in emissions can occur across many sectors (such as transportation, building energy use, and electricity generation). With the use of the Los Angeles, California, Expo Line, a framework was developed to assess how financing schemes could affect the rate of building redevelopment and resulting life-cycle GHG emissions from travel and building energy use. The framework leveraged an integrated transportation and land use life-cycle assessment model that captured upfront construction of new development near transit and the long-term changes in household energy use for travel and buildings. The results show that for the same amount of development around the Expo Line, it is possible either to meet state GHG goals by 2050 (if aggressive redevelopment happens early) or not meet those goals by 2050 (if significant redevelopment does not start for decades). The time-based approach reveals how redevelopment schedules should be considered when strategies for meeting future GHG emissions targets are set.

Frameworks for Assessing the Vulnerability of U.S. Rail Systems to Flooding and Extreme Heat

Arizona State University Report No. ASU-SSEBE-CESEM-2015-RPR-001

Recent climatic trends show more flooding and extreme heat events and in the future transportation infrastructure may be susceptible to more frequent and intense environmental perturbations. Our transportation systems have largely been designed to withstand historical weather events, for example, floods that occur at an intensity that is experience once every 100 years, and there is evidence that these events are expected become more frequent. There are increasing efforts to better understand the impacts of climate change on transportation infrastructure. An abundance of new research is emerging to study various aspects of climate change on transportation systems. Much of this research is focused on roadway networks and reliable automobile travel. We explore how flooding and extreme heat might impact passenger rail systems in the Northeast and Southwest U.S..

Transit-oriented Smart Growth Can Reduce Life-cycle Environmental Impacts and Household Costs in Los Angeles

Transport Policy, 2014, 35, pp.21-30, doi: 10.1016/j.tranpol.2014.05.004

The environmental and economic assessment of neighborhood-scale transit-oriented urban form changes should include initial construction impacts through long-term use to fully understand the benefits and costs of smart growth policies. The long-term impacts of moving people closer to transit require the coupling of behavioral forecasting with environmental assessment. Using new light rail and bus rapid transit in Los Angeles, California as a case study, a life-cycle environmental and economic assessment is developed to assess the potential range of impacts resulting from mixed-use infill development. An integrated transportation and land use life-cycle assessment framework is developed to estimate energy consumption, air emissions, and economic (public, developer, and user) costs. Residential and commercial buildings, automobile travel, and transit operation changes are included and a 60-year forecast is developed that compares transit-oriented growth against growth in areas without close access to high-capacity transit service. The results show that commercial developments create the greatest potential for impact reductions followed by residential commute shifts to transit, both of which may be effected by access to high-capacity transit, reduced parking requirements, and developer incentives. Greenhouse gas emission reductions up to 470 Gg CO2-equivalents per year can be achieved with potential costs savings for TOD users. The potential for respiratory impacts (PM10-equivalents) and smog formation can be reduced by 28–35%. The shift from business-as-usual growth to transit-oriented development can decrease user costs by $3100 per household per year over the building lifetime, despite higher rental costs within the mixed-use development.

Assessing the Potential for Reducing Life-Cycle Environmental Impacts through Transit-Oriented Development Infill along Existing Light Rail in Phoenix

Journal of Planning, Education, and Research, 2013, 33(4), 395-410, doi: 10.1177/0739456X13507485

There is significant interest in reducing urban growth impacts yet little information exists to comprehensively estimate the energy and air quality tradeoffs. An integrated transportation and land-use life-cycle assessment framework is developed to quantify the long-term impacts from residential infill, using the Phoenix light rail system as a case study. The results show that (1) significant reductions in life-cycle energy use, greenhouse gas emissions, respiratory, and smog impacts are possible; (2) building construction, vehicle manufacturing, and energy feedstock effects are significant; and (3) marginal benefits from reduced automobile use and potential household behavior changes exceed marginal costs from new rail service.

Integrating Life-cycle Environmental and Economic Assessment with Transportation and Land Use Planning

Environmental Science and Technology, 2013, 47(21), 12020-12028, doi: 10.1021/es402985g

The environmental outcomes of urban form changes should couple life-cycle and behavioral assessment methods to better understand urban sustainability policy outcomes. Using Phoenix, Arizona light rail as a case study, an integrated transportation and land use life-cycle assessment (itlulca) framework is developed to assess the changes to energy consumption and air emissions from transit-oriented neighborhood designs. Residential travel, commercial travel, and building energy use are included and the framework integrates household behavior change assessment to explore the environmental and economic outcomes of policies that affect infrastructure. The results show that upfront environmental and economic investments are needed (through more energy-intense building materials for high-density structures) to produce long run benefits in reduced building energy use and automobile travel. The annualized life-cycle benefits of transit-oriented developments in Phoenix can range from 1.7 to 230 Gg CO2e depending on the aggressiveness of residential density. Midpoint impact stressors for respiratory effects and photochemical smog formation are also assessed and can be reduced by 1.2–170 Mg PM10e and 41–5200 Mg O3e annually. These benefits will come at an additional construction cost of up to $410 million resulting in a cost of avoided CO2e at $16–29 and household cost savings.

Environmental Life Cycle Assessment of San Francisco Bay Area Muni Light Rail and Rapid Transit with Wholesale and Renewable Electricity

Arizona State University Report No. ASU-SSEBE-CESEM-2013-RPR-004

The environmental life cycle assessment of electric rail public transit modes requires an assessment of electricity generation mixes. The provision of electricity to a region does not usually adhere to geopolitical boundaries. Electricity is governed based on lowest cost marginal dispatch and reliability principles. Additionally, there are times when a public transit agency may purchase wholesale electricity from a particular service provider. Such is the case with electric rail modes in the San Francisco Bay Area. An environmental life cycle assessment of San Francisco Bay Area public transit systems was developed by Chester and Horvath (2009) and includes vehicle manufacturing/maintenance, infrastructure construction/operation/maintenance, energy production, and supply chains, in addition to vehicle propulsion. For electric rail modes, vehicle propulsion was based on an average electricity mix for the region. Since 2009, new electricity contract information and renewable electricity goals have been established. As such, updated life cycle results should be produced. Using recent wholesale electricity mix and renewable electricity goal data from the transit agencies, updated electricity precombustion, generation, transmission, and distribution environmental impacts of vehicle propulsion are estimated. In summary, SFMTA Muni light rail is currently purchasing 100% hydro electricity from the Hetch Hetchy region of California and the Bay Area Rapid Transit (BART) system is purchasing 22% natural gas, 9% coal, 2% nuclear, 66% hydro, and 1% other renewables from the Pacific Northwest . Furthermore, the BART system has set a goal of 20% renewables by 2016. Using the GREET1 2012 electricity pathway, a life cycle assessment of wholesale and renewable electricity generation for these systems is calculated.

Transit-Oriented Development Deployment Strategies to Maximize Integrated Transportation and Land Use Life Cycle Greenhouse Gas Reductions

ISSST, 2013, doi: 10.6084/m9.figshare.805094

Urban sustainability decision makers should incorporate time-based impacts of greenhouse gas emissions with life cycle assessment to improve climate change mitigation strategies. As cities develop strategies that move development closer to transit systems and encourage households to live in lower energy configurations, new methods are needed for understanding how upfront emissions of greenhouse gases produce long run radiative forcing impacts. Using an existing assessment of the development potential around Phoenix’s new light rail system, a framework is developed for deploying higher density, lower energy use, and more transit-friendly households near light rail given financing constraints. The case study compares development around transit stations in Phoenix against continued outward growth of single family homes. Using this case study, the significance of greenhouse gas (GHG) radiative forcing discounting is assessed. The radiative forcing benefits of different levels of financing aggressiveness are shown. A comparison of payback on upfront construction impacts for long run benefits is developed between the GHG accounting approach and the radiative forcing approach, the latter of which accounts for time-based GHG impacts. The results show that the radiative forcing approach puts more weight on upfront construction impacts and pushes the payback on initial investments out further than when GHG accounting is used. It is possible to reduce this payback time by providing a larger upfront financing resource. Ultimately, policy and decision makers should use radiative forcing measures over GHG measures because it will provide a measure that discounts GHG emissions at different times to a normalized unit.

Infrastructure and Automobile Shifts: Positioning Transit to Reduce Life-cycle Environmental Impacts for Urban Sustainability Goals

Environmental Research Letters, 2013, 8(1), 015041, doi: 10.1088/1748-9326/8/1/015041

Public transportation systems are often part of strategies to reduce urban environmental impacts from passenger transportation yet comprehensive energy and environmental life-cycle measures, including upfront infrastructure effects and indirect and supply chain processes, are rarely considered. Using the new bus rapid transit and light rail lines in Los Angeles, near-term and long-term life-cycle impact assessments are developed, including reduced automobile travel. Energy consumption and emissions of greenhouse gases and criteria pollutants are assessed, as well the potential for smog and respiratory impacts. Results show that life-cycle infrastructure, vehicle, and energy production components significantly increase the footprint of each mode (by 48-100% for energy and greenhouse gases, and up to 6200% for environmental impacts), and emerging technologies and renewable electricity standards will significantly reduce impacts. Life-cycle results are identified as either local (in Los Angeles) or remote and show how the decision to build and operate a transit system in a city produces environmental impacts far outside of geopolitical boundaries. Ensuring shifts of between 20-30% of transit riders from automobiles will result in passenger transportation greenhouse gas reductions for the city, and the larger the shift the quicker the payback, which should be considered for time-specific environmental goals.

Comparison of Life-cycle Energy and Emissions Footprints of Passenger Transportation in Metropolitan Regions

Atmospheric Environment, 2010, 44(8), pp. 1071-1079, doi: 10.1016/j.atmosenv.2009.12.012

A comparative life-cycle energy and emissions (greenhouse gas, CO, NOX, SO2, PM10, and VOCs) inventory is created for three U.S. metropolitan regions (San Francisco, Chicago, and New York City). The inventory captures both vehicle operation (direct fuel or electricity consumption) and non-operation components (e.g., vehicle manufacturing, roadway maintenance, infrastructure operation, and material production among others). While urban transportation inventories have been continually improved, little information exists identifying the particular characteristics of metropolitan passenger transportation and why one region may differ from the next. Using travel surveys and recently developed transportation life-cycle inventories, metropolitan inventories are constructed and compared. Automobiles dominate total regional performance accounting for 86–96% of energy consumption and emissions. Comparing system-wide averages, New York City shows the lowest end-use energy and greenhouse gas footprint compared to San Francisco and Chicago and is influenced by the larger share of transit ridership. While automobile fuel combustion is a large component of emissions, diesel rail, electric rail, and ferry service can also have strong contributions. Additionally, the inclusion of life-cycle processes necessary for any transportation mode results in significant increases (as large as 20 times that of vehicle operation) for the region. In particular, emissions of CO2 from cement production used in concrete throughout infrastructure, SO2 from electricity generation in non-operational components (vehicle manufacturing, electricity for infrastructure materials, and fuel refining), PM10 in fugitive dust releases in roadway construction, and VOCs from asphalt result in significant additional inventory. Private and public transportation are disaggregated as well as off-peak and peak travel times. Furthermore, emissions are joined with healthcare and greenhouse gas monetized externalities to evaluate the societal costs of passenger transportation in each region. Results are validated against existing studies. The dominating contribution of automobile end-use energy consumption and emissions is discussed and strategies for improving regional performance given private travel's disproportionate share are identified.

Environmental Assessment of Passenger Transportation Should Include Infrastructure and Supply Chains

Environmental Research Letters, 2009, 4(2), doi: 10.1088/1748-9326/4/2/024008

To appropriately mitigate environmental impacts from transportation, it is necessary for decision makers to consider the life-cycle energy use and emissions. Most current decision-making relies on analysis at the tailpipe, ignoring vehicle production, infrastructure provision, and fuel production required for support. We present results of a comprehensive life-cycle energy, greenhouse gas emissions, and selected criteria air pollutant emissions inventory for automobiles, buses, trains, and airplanes in the US, including vehicles, infrastructure, fuel production, and supply chains. We find that total life-cycle energy inputs and greenhouse gas emissions contribute an additional 63% for onroad, 155% for rail, and 31% for air systems over vehicle tailpipe operation. Inventorying criteria air pollutants shows that vehicle non-operational components often dominate total emissions. Life-cycle criteria air pollutant emissions are between 1.1 and 800 times larger than vehicle operation. Ranges in passenger occupancy can easily change the relative performance of modes.

Life-cycle Energy and Emissions Inventories for Motorcycles, Diesel Automobiles, School Buses, Electric Buses, Chicago Rail, and New York City Rail

University of California, Berkeley Report No. UCB-ITS-VWP-2009-2

The development of life-cycle energy and emissions factors for passenger transportation modes is critical for understanding the total environmental costs of travel. Previous life-cycle studies have focused on the automobile given its dominating share of passenger travel and have included only few life-cycle components, typically related to the vehicle (i.e., manufacturing, maintenance, end-of-life) or fuel (i.e., extraction, refining, transport). Chester (2009) provides the first comprehensive environmental life-cycle assessment of not only vehicle and fuel components but also infrastructure components for automobiles, buses, commuter rail systems, and aircraft. Many processes were included for vehicles (manufacturing, active operation, inactive operation, maintenance, insurance), infrastructure (construction, operation, maintenance, parking, insurance), and fuels (production, distribution) in Chester (2009). The vehicles inventoried were sedans, pickups, SUVs, urban diesel buses, light rail (San Francisco’s Muni Metro and Boston’s Green Line, both electric), heavy rail (San Francisco Bay Area’s BART and Caltrain), and aircraft (small, medium, and large-sized planes are disaggregated). Given the methodological framework in Chester (2009), the question of applicability of these systems to other U.S. modes, and the data availability of other modes, is extended in this study to motorcycles, light duty diesel vehicles, school buses, electric buses, Chicago commuter rail modes, and New York City commuter rail modes.