Publications, Reports, and Media

Proceedings of the 2015 Transportation Research Board 94th Annual Meeting (Paper 15-4940)

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 complex systems are accurately communicated. California’s greenhouse gas (GHG) reduction policies have created interest in better understanding how public transit systems reduce emissions. An LCA is developed of the Los Angeles Expo line and a competing car trip that includes vehicle, infrastructure, and energy production processes, in addition to propulsion. Energy use, GHG emissions, and the potential for photochemical smog formation and respiratory impacts are assessed. When results are normalized per passenger kilometer traveled (PKT), life-cycle processes increase impacts by up to 83% for energy use and GHG emissions, and up to 690% for smog and respiratory impact potentials. However, the use of a non-time-based 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 reduction 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. The line can be expected to breakeven on GHG emissions within two decades but its ability meet long-run policy targets is most sensitive to infrastructure construction emissions, mode shifting, a changing electricity mix, and improving automobile fuel economy.

Proceedings of the 2015 Transportation Research Board 94th Annual Meeting (Paper 15-5007)

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.

This manuscript builds on our UCLA Institute of Transportation Studies report Cost-Effectiveness of Reductions in Greenhouse Gas Emissions from California High-Speed Rail and Urban Transportation Projects.

Proceedings of the 2015 Transportation Research Board 94th Annual Meeting (Paper 15-0254)

Cities are increasingly developing greenhouse gas (GHG) mitigation plans and reduction targets based on 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). Even more complicated is when cities focus on achieving GHG reductions through integrated transportation and land use planning, as changes in emissions can occur across many sectors (such as transportation, building energy use, and electricity generation). Using the Los Angeles Expo line, a framework is developed to assess how financing schemes change the rate of redevelopment and resulting life-cycle GHG emissions from travel and building energy use. The framework leverages an integrated transportation and land use life-cycle assessment model that captures 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 to either meet (if aggressive redevelopment happens early) or not meet (if redevelopment starts decades out) state GHG goals by 2050. The time-based approach reveals how specific redevelopment schedules are needed for a city to reduce GHG emissions at a rate that meets future targets.

Worldwide Greenhouse Gas Reduction Potentials in Transportation by 2050

Journal of Industrial Ecology, Volume and Issue Forthcoming.

Passenger and freight transport are one of the world’s leading contributors of anthropogenic carbon dioxide and other greenhouse gas (GHG) emissions. It has been suggested that the world can reduce the GHG-intensity of the transportation sector in the future through the adoption of new fuel-saving technologies, switching demand between modes, and large-scale implementation of alternative fuels. The future scenarios presented in this study assess the GHG reduction potentials of policies related to these three strategies for major passenger and freight modes across 8 regions of the world. We find that new fuel-saving technologies can significantly reduce the life-cycle GHG footprint of both passenger and freight vehicles. However, this improved fuel efficiency has negative feedbacks to the effectiveness of mode-switching and alternative fuel adoption policies through 2050. Our results suggest that improvements in the fuel efficiency of vehicles alone may cause the marginal benefits of GHG abatement policies to diminish over time. However, this trend may be opposite if the rate at which alternative fuel pathways decarbonize at faster rates than conventional transportation fuels (e.g., petroleum based). Overall, we find that the largest opportunities for GHG reductions occur in non-OECD countries. Given the many factors that distinguish transportation systems within these countries from the rest of the world (e.g., individual access to financial resources, control over infrastructure, systems to maintain new technologies, etc.), many benefits could be gained through interregional cooperation.

Goods Movement Life-cycle Assessment for Greenhouse Gas Reduction Goals

Journal of Industrial Ecology, Volume and Issue Forthcoming, doi: 10.1111/jiec.12277.

The formation of effective policies to reduce emissions from goods movement should consider local and remote life-cycle effects as well as barriers for mode shifting. Using uni- and multi-modal freight movements by truck, rail, and ocean-going vessel associated with California, a life-cycle assessment (LCA) is developed to estimate the local and remote emissions that occur from freight activity inside and associated with the state. Long-run average per tonne-km results show that ocean going vessels emit the fewest emissions, followed by rail, then trucks, and that the inclusion of life-cycle processes can increase impacts by up to 32% for energy and GHG emissions and 4,200% for conventional air pollutants. Efforts to reduce emissions through mode shifting should recognize that infrastructure and market configurations may be inimical to mode substitution. A uni- and multi-modal shipping emissions assessment is developed for intrastate and California-associated freight movements to illustrate the life-cycle impacts of typical trips for certain types of goods. When targeting greenhouse gas reductions in California it should be recognized that heavy-duty trucks are responsible for 99% of intrastate goods movement emissions. An assessment of future freight truck technology improvements is performed to estimate the effectiveness of strategies to meet 2050 greenhouse gas reduction goals. While aggressive improvements in fuel economy coupled with alternative vehicles and fuels can significantly reduce GHG emissions, to meet 2050 goals will likely require zero carbon emission vehicle technology. The value of using LCA in GHG reduction policy for transportation systems is explored.

Metropolitan greenhouse gas and air emissions inventories can better account for the variability in vehicle movement, fleet composition, and infrastructure that exists within and between regions, to develop more accurate information for environmental goals. With emerging access to high quality data, new methods are needed for informing transportation emissions assessment practitioners of the relevant vehicle and infrastructure characteristics that should be prioritized in modeling to improve the accuracy of inventories. The sensitivity of light and heavy-duty vehicle greenhouse gas (GHG) and conventional air pollutant (CAP) emissions to speed, weight, age, and roadway gradient are examined with second-by-second velocity profiles on freeway and arterial roads under free-flow and congestion scenarios. For GHG and CAP upper and lower bounds of each factor show the potential variability which could exist in emissions assessments across U.S. cities. When comparing the effects of changes in these characteristics across U.S. cities against average characteristics of the U.S. fleet and infrastructure, significant variability in emissions is found to exist. GHGs from light-duty vehicles could vary by -2%-11% and CAP by -47%-228% when compared to the baseline. For heavy-duty vehicles the variability is -21%-55% and -32%-174%, respectively. The results show that cities should more aggressively pursue the integration of emerging big data into regional transportation emissions modeling, and the integration of these data is likely to impact GHG and CAP inventories and how aggressively policies should be implemented to meet reductions. A web-tool (available at is developed to aide cities in improving emissions uncertainty.

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.

A methodology is developed that integrates institutional analysis with Life Cycle Assessment (LCA) to identify and overcome barriers to sustainability transitions and to bridge the gap between environmental practitioners and decisionmakers. LCA results are rarely joined with analyses of the social systems that control or influence decisionmaking and policies. As a result, LCA conclusions generally lack information about who or what controls different parts of the system, where and when the processes' environmental decisionmaking happens, and what aspects of the system (i.e. a policy or regulatory requirement) would have to change to enable lower environmental impact futures. The value of the combined institutional analysis and LCA (the IA-LCA) is demonstrated using a case study of passenger transportation in the Phoenix, Arizona metropolitan area. A retrospective LCA is developed to estimate how roadway investment has enabled personal vehicle travel and its associated energy, environmental, and economic effects. Using regional travel forecasts, a prospective life cycle inventory is developed. Alternative trajectories are modeled to reveal future "savings" from reduced roadway construction and vehicle travel. An institutional analysis matches the LCA results with the specific institutions, players, and policies that should be targeted to enable transitions to these alternative futures. The results show that energy, economic, and environmental benefits from changes in passenger transportation systems are possible, but vary significantly depending on the timing of the interventions. Transition strategies aimed at the most optimistic benefits should include 1) significant land-use planning initiatives at the local and regional level to incentivize transit-oriented development infill and urban densification, 2) changes to state or federal gasoline taxes, 3) enacting a price on carbon, and 4) nearly doubling vehicle fuel efficiency together with greater market penetration of alternative fuel vehicles. This aggressive trajectory could decrease the 2050 energy consumption to 1995 levels, greenhouse gas emissions to 1995, particulate emissions to 2006, and smog-forming emissions to 1972. The potential benefits and costs are both private and public, and the results vary when transition strategies are applied in different spatial and temporal patterns.

Los Angeles is often presented as the epitome of post-automobile sprawling urban growth. There tends to be a somewhat unclear understanding of why the city has grown the way it has. We explore the deployment of infrastructure as an enabler of growth, for better or worse. Presented below is an animation of the deployment of the Los Angeles Roadway network, from 1990 to present. This is part of a research project that is exploring the cost, energy, and greenhouse gas impacts of transportation systems and how embedded infrastructure enable unsustainable emergent behaviors. Over the next few months, we will update this video as we finalize our cost, energy, and greenhouse gas results.

Growth of the Los Angeles Roadway Network from Mikhail Chester on Vimeo.

Grand Challenges for High-speed Rail Environmental Assessment in the United States

Transportation Research Part A: Policy and Practice, 2014, 61, 15-26, doi: 10.1016/j.tra.2013.12.007.

The comprehensiveness of environmental assessments of future long-distance travel that include high-speed rail (HSR) are constrained by several methodological, institutional, and knowledge gaps that must and can be addressed. These gaps preclude a robust understanding of the changes in environmental, human health, resource, and climate change impacts that result from the implementation of HSR in the United States. The gaps are also inimical to an understanding of how HSR can be positioned for 21st century sustainability goals. Through a synthesis of environmental studies, the gaps are grouped into five overarching grand challenges. They include a spatial incompatibility between HSR and other long-distance modes that is often ignored, an environmental review process that obviates modal alternatives, siloed interest in particular environmental impacts, a dearth of data on future vehicle and energy sources, and a poor understanding of secondary impacts, particularly in land use. Recommendations are developed for institutional investment in multimodal research, knowledge and method building around several topics. Ultimately, the environmental assessment of HSR should be integrated in assessments that seek to understand the complementary and competitive configurations of transportation services, as well as future accessibility.

The growth of the Phoenix roadway network developed through a combined roadway link and travel analysis zone statistical assessment of building ages. Infrastructure has been constructed ahead of and in concert with sprawling edge growth. Half of the current roadways were constructed after 1979 at the edges of the urbanized area (i.e., the 101, 202, and 303 loops)..

Growth of the Los Angeles Roadway Network from Mikhail Chester on Vimeo.

Life-cycle Assessment for Construction of Sustainable Infrastructure

ASCE Practice Periodical on Structural Design and Construction, 2014, 19(1), 89-94, doi: 10.1061/(ASCE)SC.1943-5576.0000187.

The architecture-engineering-construction (AEC) industry faces increasing demands on its projects while budgets appear to be shrinking. Building owners and operators seem to want their buildings to do more for less cost. Although this may seem counterintuitive, it aligns nicely with a sustainable-architecture approach of less is more. Moreover, in a shift from exclusively considering first costs for a project, the AEC industry seems to be moving in the direction of life-cycle cost considerations, furthering the opportunity for a more sustainable built environment. Often sustainable is synonymous with achieving certification [e.g., Leadership in Energy and Environmental Design (LEED) and Infrastructure Voluntary Evaluation Sustainability Tool (INVEST) certification]. Whereas the authors acknowledge that certification can improve particular aspects of sustainability, it is necessary to take a broader approach and consider economic, environmental, and social dimensions of sustainability. In this paper, the authors explore each of these dimensions and present examples of how the AEC industry can measure, balance, and monetize them.

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.

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.

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.

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.

There is significant experience and research on the competition and complementarity of air and high-speed rail (HSR) modes. In synthesizing the body of literature, reviewers focused on government-driven environmental comparisons and academic literature. Both government environmental reviews and academic studies have provided valuable insight into comparative assessments of air and HSR systems; however, institutional mechanisms coupled with methodological advances and tool development are needed to ensure that future long-distance transportation systems are deployed in ways that minimize impacts while improving mobility.

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.

Figures and Data:
Figure Data
Figure 1: Life-cycle per Passenger Mile Traveled Results for Average Occupancy Vehicles
Figure 2: Environmental Impact Schedules and Resulting Paybacks
Figure 3: Transit Energy and Environmental Payback Speed with Automobile Shifts
Figure 4: Life-cycle Door-to-door Greenhouse Gas Comparison

Media Coverage and Related Documents:
Environmental Research Web: Public-transit systems improve urban environment
Policy Brief
LA Metro's Blog The Source
ERL Perspective by Matt Eckelman: Life Cycle Assessment in Support of Sustainable Transportation

Comparative Environmental Life Cycle Assessment of Conventional and Electric Vehicles

Journal of Industrial Ecology, 2013, 17(1), pp.53-64, doi: 10.1111/j.1530-9290.2012.00532.x

Electric vehicles (EVs) coupled with low-carbon electricity sources offer the potential for reducing greenhouse gas emissions and exposure to tailpipe emissions from personal transportation. In considering these benefits, it is important to address concerns of problem-shifting. In addition, while many studies have focused on the use phase in comparing transportation options, vehicle production is also significant when comparing conventional and EVs. We develop and provide a transparent life cycle inventory of conventional and electric vehicles and apply our inventory to assess conventional and EVs over a range of impact categories. We find that EVs powered by the present European electricity mix offer a 10% to 24% decrease in global warming potential (GWP) relative to conventional diesel or gasoline vehicles assuming lifetimes of 150,000 km. However, EVs exhibit the potential for significant increases in human toxicity, freshwater eco-toxicity, freshwater eutrophication, and metal depletion impacts, largely emanating from the vehicle supply chain. Results are sensitive to assumptions regarding electricity source, use phase energy consumption, vehicle lifetime, and battery replacement schedules. Because production impacts are more significant for EVs than conventional vehicles, assuming a vehicle lifetime of 200,000 km exaggerates the GWP benefits of EVs to 27% to 29% relative to gasoline vehicles or 17% to 20% relative to diesel. An assumption of 100,000 km decreases the benefit of EVs to 9% to 14% with respect to gasoline vehicles and results in impacts indistinguishable from those of a diesel vehicle. Improving the environmental profile of EVs requires engagement around reducing vehicle production supply chain impacts and promoting clean electricity sources in decision making regarding electricity infrastructure.

Getting the Most Out of Electric Vehicle Subsidies

Issues in Science and Technology

The electrification of passenger vehicles has the potential to address three of the most critical challenges of our time: Plug-in vehicles may produce fewer greenhouse gas emissions when powered by electricity instead of gasoline, depending on the electricity source; reduce and displace tailpipe emissions, which affect people and the environment; and reduce gasoline consumption, helping to diminish dependence on imported oil and diversify transportation energy sources. When all costs are added up, we find thousands of dollars of damages per vehicle (gasoline or electric) that are paid by the overall population rather than only by those releasing the emissions and consuming the oil. These costs are substantial. But, importantly, the potential of plug-in vehicles to reduce these costs is modest: much lower than the $7,500 tax credit and small compared to ownership costs. This is because the damages caused over the life cycle of a vehicle are caused not only by gasoline consumption, which is reduced with plug-in vehicles, but also by emissions from battery and electricity production, which are increased with plug-in vehicles.

Sustainable mobility policy for long-distance transportation services should consider emerging automobiles and aircraft as well as infrastructure and supply chain life-cycle effects in the assessment of new high-speed rail systems. Using the California corridor, future automobiles, high-speed rail and aircraft long-distance travel are evaluated, considering emerging fuel-efficient vehicles, new train designs and the possibility that the region will meet renewable electricity goals. An attributional per passenger-kilometer-traveled life-cycle inventory is first developed including vehicle, infrastructure and energy production components. A consequential life-cycle impact assessment is then established to evaluate existing infrastructure expansion against the construction of a new high-speed rail system. The results show that when using the life-cycle assessment framework, greenhouse gas footprints increase significantly and human health and environmental damage potentials may be dominated by indirect and supply chain components. The environmental payback is most sensitive to the number of automobile trip takers shifted to high-speed rail and for greenhouse gases is likely to occur in 20–30 years. A high-speed rail system that is deployed with state-of-the-art trains, electricity that has met renewable goals, and in a configuration that endorses high ridership will provide significant environmental benefits over existing modes. Opportunities exist for reducing the long-distance transportation footprint by incentivizing large automobile trip shifts, meeting clean electricity goals and reducing material production effects.

Media Coverage:
 Environmental Research Web
 Arizona State University Press Release and Engineering News
 University of California, Berkeley Press Release and Transportation News
Articles:  KPBS  -  Phys Org  -  KQED  -  R&D

Costs of Automobile Air Emissions in U.S. Metropolitan Areas

Transportation Research Record (TRR), 2011, 2233, pp.120-127, doi: 10.3141/2233-14

Automobile air emissions are a well recognized problem and have been subject to considerable regulation. An increasing concern for greenhouse gas emissions draws additional considerations to the externalities of personal vehicle travel. In this paper, we estimate automobile air emission costs for eighty-six U.S. metropolitan areas based on county-specific external air emission morbidity, mortality, and environmental costs. Total air emission costs in the urban areas are estimated to be $145 million/day, with Los Angeles and New York (each $23 million/day) having the highest totals. These external costs average $0.64/day/person and $0.03/vehicle mile traveled. Total air emission cost solely due to traffic congestion for the same eight-six U.S. metropolitan areas was also estimated to be $24 million/day. We compare our estimates with others found in the literature and find them to be generally consistent. These external automobile air emission costs are important for social benefit and cost assessment of transportation measures to reduce vehicle use. However, this study does not include any abatement costs associated with automobile emission controls or government investments to reduce emissions such as traffic signal setting.

Are Plug-in Vehicles Worth the Cost?

Proceedings of the National Academy of Sciences (PNAS), 2011, 108(40), doi: 10.1073/pnas.1104473108

We assess the economic value of life cycle air emissions and oil consumption from conventional, hybrid-electric (HEVs), plug-in hybrid electric (PHEV), and battery electric vehicles in the U.S. We find that plug-in vehicles may reduce or increase externality costs relative to grid-independent HEVs, depending largely on greenhouse gas and SO2 emissions produced during vehicle charging and battery manufacturing. However, even if future marginal damages from emissions of battery and electricity production drop dramatically, the damage reduction potential of plug-in vehicles remains small compared to ownership cost. As such, to offer a socially efficient approach to emissions and oil consumption reduction, lifetime cost of plug-in vehicles must be competitive with HEVs. Current subsidies intended to encourage sales of plug-in vehicles with large capacity battery packs exceed our externality estimates considerably, and taxes that optimally correct for externality damages would not close the gap in ownership cost. In contrast, HEVs and PHEVs with small battery packs reduce externality damages at low (or no) additional cost over their lifetime. While large battery packs allow vehicles to travel longer distances using electricity instead of gasoline, large packs are more expensive, heavier, and more emissions-intensive to produce, with lower utilization factors, greater charging infrastructure requirements, and life cycle implications that are more sensitive to uncertain, time-sensitive, and location-specific factors. To reduce air emission and oil dependency impacts from passenger vehicles, strategies to promote adoption of HEVs and PHEVs with small battery packs offer more social benefits per dollar spent.

Media Coverage:
 Carnegie Mellon University Press Release   (Reprinted by the Sacramento Bee)
 Arizona State University Press Release
 Bloomberg: U.S. Battery, Plug-in Car Push Costs Exceed Rewards, New Study Says
 Vancouver Sun: Fully electric vehicles fall short compared to hybrids, research suggests
 Automotive News: U.S. green car subsidies aren't cost effective, study says

Little is known about how parking infrastructure affects energy demand, the environment and the cost of vehicle travel. Passenger and freight movements are often the focus of energy and environmental assessments, but vehicles spend most of their lives parked. Abundant free parking encourages vehicle travel and is thus a major incentive to auto travel and urban congestion. Abundant free parking also discourages public transit, walking, and biking. The technique of transportation life-cycle assessment (LCA) allows us to understand the full costs of travel including the energy use and environmental effects of parking infrastructure. Past LCAs, however have focused on evaluating the resources used for travel and have ignored resources use for parking. This focus is understandable given the diversity of parking spaces and the lack of available data on parking infrastructure. For example, consider the great differences in energy use and emissions associated with a curb parking spaces, multi-story garages, and private home garages. Furthermore, because causality between parking supply and automobile travel flows occurs in both directions, determining the energy use and environmental effects of a specific automobile trip (say a strip mall) is not possible. We develop a range of estimates of the U.S. parking space inventory, determine construction and maintenance energy use and environmental effects, and evaluate these results in the life-cycle of automobile travel. We find that the for many vehicle trips the environmental effects of the parking infrastructure sometimes equal or exceed the environmental effects of the vehicles themselves.

(Note: this article focuses on the policy implications of our Environmental Research Letter's publication Parking Infrastructure: Energy, Emissions, and Automobile Life-cycle Environmental Accounting)

California is planning to spend $40 billion to build a high speed rail system from San Diego to Sacramento. Advocates argue that high speed rail will save money and improve the environment, while critics claim it will waste money and harm the environment. What accounts for these diametrically opposed views about a technology that has been operating in other countries for decades? And what can transportation analysts offer to inform the debate? Disagreements about the cost and environmental impacts of high speed rail can arise when analysts examine only the most direct effects of the rail system, and compare those to only the direct effects of road and air travel—-the two transportation modes from which high speed rail will likely draw passengers. But transportation energy use and emissions result not only from the direct effects of operating the vehicles but also from indirect effects, such as building the infrastructure, producing the fuels, manufacturing the vehicles, maintaining the system, and disposing of materials at the end of their lives. The full range of emissions from automobile travel, for example, includes not only tailpipe emissions but also the emissions created by building roads and parking garages, manufacturing cars, extracting and refining petroleum, and, finally, wrecking yards and tire dumps. One approach to environmental and cost-benefit analysis that takes both these direct and indirect effects into account is life-cycle assessment. In this article we use life-cycle assessment to compare the energy use and pollution emissions of high speed rail and its competing modes.

(Note: this article focuses on the policy implications of our Environmental Research Letter's publication Parking Infrastructure: Energy, Emissions, and Automobile Life-cycle Environmental Accounting)

The US parking infrastructure is vast and little is known about its scale and environmental impacts. The few parking space inventories that exist are typically regionalized and no known environmental assessment has been performed to determine the energy and emissions from providing this infrastructure. A better understanding of the scale of US parking is necessary to properly value the total costs of automobile travel. Energy and emissions from constructing and maintaining the parking infrastructure should be considered when assessing the total human health and environmental impacts of vehicle travel. We develop five parking space inventory scenarios and from these estimate the range of infrastructure provided in the US to be between 105 million and 2 billion spaces. Using these estimates, a life-cycle environmental inventory is performed to capture the energy consumption and emissions of greenhouse gases, CO, SO2, NOX, VOC (volatile organic compounds), and PM10 (PM: particulate matter) from raw material extraction, transport, asphalt and concrete production, and placement (including direct, indirect, and supply chain processes) of space construction and maintenance. The environmental assessment is then evaluated within the life-cycle performance of sedans, SUVs (sports utility vehicles), and pickups. Depending on the scenario and vehicle type, the inclusion of parking within the overall life-cycle inventory increases energy consumption from 3.1 to 4.8 MJ by 0.1–0.3 MJ and greenhouse gas emissions from 230 to 380 g CO2e by 6–23 g CO2e per passenger kilometer traveled. Life-cycle automobile SO2 and PM10 emissions show some of the largest increases, by as much as 24% and 89% from the baseline inventory. The environmental consequences of providing the parking spaces are discussed as well as the uncertainty in allocating paved area between parking and roadways.

The state of California is expected to have significant population growth in the next half-century resulting in additional passenger transportation demand. Planning for a high-speed rail system connecting San Diego, Los Angeles, San Francisco, and Sacramento as well as many population centers between is now underway. The considerable investment in California high-speed rail has been debated for some time and now includes the energy and environmental tradeoffs. The per-trip energy consumption, greenhouse gas emissions, and other emissions are often compared against the alternatives (automobiles, heavy rail, and aircraft), but typically only considering vehicle operation. An environmental life-cycle assessment of the four modes was created to compare both direct effects of vehicle operation and indirect effects from vehicle, infrastructure, and fuel components. Energy consumption, greenhouse gas emissions, and SO2, CO, NOX, VOC, and PM10 emissions were evaluated. The energy and emission intensities of each mode were normalized per passenger kilometer traveled by using high and low occupancies to illustrate the range in modal environmental performance at potential ridership levels. While high-speed rail has the potential to be the lowest energy consumer and greenhouse gas emitter, appropriate planning and continued investment would be needed to ensure sustained high occupancy. The time to environmental payback is discussed highlighting the ridership conditions where high-speed rail will or will not produce fewer environmental burdens than existing modes. Furthermore, environmental tradeoffs may occur. High-speed rail may lower energy consumption and greenhouse gas emissions per trip but can create more SO2 emissions (given the current electricity mix) leading to environmental acidification and human health issues. The significance of life-cycle inventorying is discussed as well as the potential of increasing occupancy on mass transit modes.

(Note: the high-speed rail results of this study supplant those presented in "Life-cycle Environmental Inventory of Passenger Transportation Modes in the United States" as well as vwp-2008-2 and vwp-2007-7.)

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.

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.

(Note: the results of this study supplant those presented in "Life-cycle Environmental Inventory of Passenger Transportation Modes in the United States" as well as vwp-2008-2 and vwp-2007-7.)

Evaluation of Life-Cycle Air Emission Factors of Freight Transportation

Environ. Sci. Technol., 2007, 41 (20), pp 7138–7144 doi: 10.1021/es070989q

Life-cycle air emission factors associated with road, rail, and air transportation of freight in the United States are analyzed. All life-cycle phases of vehicles, infrastructure, and fuels are accounted for in a hybrid life-cycle assessment (LCA). It includes not only fuel combustion, but also emissions from vehicle manufacturing, maintenance, and end of life, infrastructure construction, operation, maintenance, and end of life, and petroleum exploration, refining, and fuel distribution. Results indicate that total life-cycle emissions of freight transportation modes are underestimated if only tailpipe emissions are accounted for. In the case of CO2 and NOx, tailpipe emissions underestimate total emissions by up to 38%, depending on the mode. Total life-cycle emissions of CO and SO2 are up to seven times higher than tailpipe emissions. Sensitivity analysis considers the effects of vehicle type, geography, and mode efficiency on the final results. Policy implications of this analysis are also discussed. For example, while it is widely assumed that currently proposed regulations will result in substantial reductions in emissions, we find that this is true for NOx emissions, because fuel combustion is the main cause, and to a lesser extent for SO2, but not for PM10 emissions, which are significantly affected by the other life-cycle phases.

Environmental Assessment of Freight Transportation in the U.S.

Int. J. of Life Cycle Assessment, 2006, 11(4), pp. 229-239, doi: 10.1065/lca2006.02.244.

This study provides a life cycle inventory of air emissions (CO2, NOx, PM10, and CO) associated with the transportation of goods by road, rail, and air in the U.S. It includes the manufacturing, use, maintenance, and end-of-life of vehicles, the construction, operation, maintenance, and end-of-life of transportation infrastructure, as well as oil exploration, fuel refining, and fuel distribution.

Transportation Choices and Air Pollution Effects of Telework.

J. of Infrastructure Systems, 2006, ASCE, 12(2), pp. 121-134, doi: 10.1061/(ASCE)1076-0342(2006)12:2(121).

Telework has emerged as a possible solution to transportation-related air pollution problems. This paper analyzes, both deterministically and probabilistically, a California-based 1-day telework scenario, and explores how the mode of transportation and other parameters such as vehicle miles traveled, vehicle model, occupancy rate, telecommuting frequency, and season (heating or cooling) affect the air pollution effects of telework programs when energy consumption-related emissions due to heating, cooling, lighting, and the use of electronic and electrical equipment (in the home and company office) are accounted for. Among others, the study found that total telework-related CO2 emissions during the cooling season and SO2, NO\dx, and hydrocarbon emissions in both seasons appear to be lower than nontelework emissions for all modes of transportation (except for light rail with higher NO\dx emissions and urban transit buses with roughly equal NO\dx emissions in the heating season). Light rail also has higher telework N2O and CH4 emissions. However, given the uncertainties in the data, the differences may be negligible. Urban transit buses and commuter express buses were found to be associated with more telework than nontelework CO emissions in both seasons. For these two modes, telework PM10 emissions are higher in the cooling and about the same in the heating season than nontelework emissions. Natural gas-powered ferries have more telework PM10 emissions than nontelework emissions. The study also found that for low-frequency telework programs energy use impacts could overturn transportation-related emission reductions independent of the mode of transportation used. Avoiding more polluting modes of transportation, increasing occupancy rates, substituting longer commutes and especially increasing telecommuting frequency could counteract these negative effects.

Environmental Assessment of Logistics Outsourcing

J. of Management in Engineering, 2005, ASCE, 21(1), pp. 27-37, doi: 10.1061/(ASCE)0742-597X(2005)21:1(27).

Environmental awareness is increasingly important to society, government, and industry, and there is a strong demand for sustainable development practices. The importance of supply chain management is critical, as it characterizes and influences the life cycles of all products. Within the major logistics trends, outsourcing has a significant potential to increase sustainability in the supply chain as third-party logistics providers (3PLs) focus on improving resource utilization and making processes more efficient. However, their motivation is largely economic, and an environmental perspective is rarely seen in 3PLs. As consumers demand greener alternatives and, subsequently, environmental regulatory measures are implemented, 3PLs will have to become more environmentally and socially aware in order to develop sustainability goals. This study compares two scenarios using life-cycle assessment (LCA): one where logistics functions are handled in-house, and an alternative scenario where such functions are outsourced to a 3PL. The impacts of logistics outsourcing on energy utilization, global warming potential, and fatalities are first quantified in the supply chain of an automobile. Even though vehicle operation, responsible for most of the impacts considered, is outside the domain of logistics functions, logistics outsourcing nonetheless has the potential to reduce energy use and global warming potential by 0.4–2% and fatalities by 0.8–3.3% throughout the entire life cycle of a typical automobile. Road and air transportation are found to account for most of the impacts in all selected metrics. Analyzing logistics outsourcing in the other sectors of the U.S. economy revealed the same trend as observed in the supply chain of an automobile.

Energy-related Emissions from Telework

Environmental Science & Technology, 2003, 37(16), pp. 3467-3475, doi: 10.1021/es025849p.

Telework is a growing phenomenon that is thought to save energy and air emissions. This paper applies a systems model to telework and nontelework scenarios in order to quantify greenhouse gas and other air emissions from transportation, heating, cooling, lighting, and electronic and electrical equipment use both at the company and the home office. Using United States data, a WWW-based, scalable decision-support tool was created to evaluate the environmental impacts of teleworkers. For a typical case reflecting United States teleworker patterns, the analysis found that telework has the potential to reduce air emissions. However, Monte Carlo simulation employed to perform a probabilistic analysis over a set of likely parameters has revealed that telework may not affect equally the emissions of all types of pollutants. It may decrease CO2, NOx, SO2, PM10, and CO but not N2O and CH4 emissions. Therefore, the scope and goal of telework programs must be defined early in the implementation process. Work-related transportation (commuting) impacts could be reduced as a result of telework; however, home-related impacts due to an employee spending additional time at home could potentially offset these reductions. Company office-related impacts may not be reduced unless the office space is shared with other employees during telework days or eliminated entirely. In states with high telework potential (California, Georgia, Illinois, New York, Texas), telework could save emissions, but it would depend on commuting and climatic patterns and the electricity mix. Environmentally beneficial telework programs are found to depend mainly on commuting patterns, induced energy usage, and characteristics of the office and home space and equipment use.

External Costs of Air Emissions from Transportation

J. of Infrastructure Systems, ASCE, 2001, 7(1), pp. 13-17, doi: 10.1061/(ASCE)1076-0342(2001)7:1(13).

The production of equipment and materials used for transportation facilities and services can have significant environmental effects. Considerable effort is expended to reduce such effects as efficiently and effectively as possible. In this paper, we estimate external environmental costs resulting from the production of common transportation equipment, materials, and services. These external cost estimates only include the effects from air emissions of conventional pollutants, including carbon monoxide, greenhouse gases (or global warming potential), volatile organics, sulfur dioxide, particulate matter, and nitrogen oxides. The estimates include all the direct and indirect supply chain emissions, such as electricity generation and mining. The cost estimates are uncertain and are likely to be underestimates of total external costs. However, the estimates should be useful for an initial assessment of the total social costs of transportation projects, and to indicate products and processes worthy of additional pollution prevention efforts. In particular, we find that additional external environmental costs may range from as low as 1% to as high as 45% for transportation services. External environmental costs of transportation equipment manufacturing range between 0.3 and 11%, while the external environmental costs of transportation construction and operation materials are estimated to vary between 1 and 100%.