UC Davis Institute of Transportation Studies

The processes in the pavement life cycle can be defined as: material extraction and production; construction; transport of materials and demolition; the use stage, where the pavement interacts with other systems; the materials, construction, and transport associated with maintenance and rehabilitation; and end-of-life. Local governments are increasingly being asked to quantify greenhouse gas emissions from their operations and identify changes to reduce emissions. There are many possible strategies that local governments can choose to reduce their emissions, however, prioritization and selection of which to implement can be difficult if emissions cannot be quantified. Pavement life cycle assessment (LCA) can be used by local governments to achieve the same goals as state government. The web-based software environmental Life Cycle Assessment for Pavements, also known as eLCAP has been developed a project-level LCA tool. The goal of eLCAP is to permit local governments to perform project-level pavement LCA using California specific data, including consideration of their own designs, materials, and traffic. eLCAP allows modeling of materials, transport, construction, maintenance, rehabilitation, and end-of-life recycling for all impacts; and in the use stage it considers the effects of combustion of fuel in vehicles as well as the additional fuel consumed due to pavement-vehicle interaction (global warming potential only). This report documents eLCAP and a project that created an interface for eLCAP that is usable by local governments.

This report examines the electrification of buses, vocational trucks, and construction machinery, as well as the impact of advancements in battery technology on this transition. The electrification of these vehicles and machinery, alongside rapid progress in battery development, is accelerating. This study provides a comprehensive review of current research on lithium-ion and sodium-ion batteries, evaluating their development status and the challenges to commercialization. A keyobjective of this study is to assess the progress of advanced battery development and its influence on the further commercialization of buses, vocational trucks, and construction machinery. Modeling suggests that within the next 7 to 12 years, batteries with energy densities of 500 Wh/kg and 1000 Wh/L will enable electrified construction vehicles andmachinery to match or surpass the performance of current diesel-powered equipment. Electric buses are already commercially available and expanding globally, while electrified construction trucks and machinery have been successfully demonstrated in real-world projects across the U.S., China, and Europe. These electrified machines offer multiple advantages, including lower carbon dioxide (CO₂) emissions, improved efficiency, quieter operation, and reduced maintenance and energy costs compared to diesel-powered counterparts. Manufacturers are optimistic about marketgrowth, particularly given the support of federal and state incentives aimed at reducing CO₂ emissions. Currently, the cost of electrified construction machinery remains relatively high. However, near-term cost projections are uncertain, as they depend not only on the comparative costs of diesel engines, batteries, and electric motors but also on the rate at which prices for electrical components decline in the near future. 

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Transportation access is a significant issue in low-income, rural, and otherwise underserved communities in the US, with few affordable and reliable alternatives to car ownership. Carsharing is one promising alternative to improve access among marginalized communities. Grant programs in California have funded pilot electric carshare services. But little is known about the long-term financial sustainability of these services and how their costs and revenues compare those of transit. In this study, a financial model was used to estimate the net operating income (fare revenue minus costs) for Míocar, an electric carsharing service in marginalized suburban and rural communities. The estimated net operating income per month was −$1561, under current operating conditions, and ranged from −$1255 to −$1623 depending on simulated changes to fleet size, pricing, and usage rates. These negative net operating incomes correspond to a shortfall (or need for subsidies) of 68% to 92% of operational costs. Míocar could achieve a higher ratio of fare revenues to operational costs (13%) than existing transit (3 to 8%). To minimize required subsidies, electric carshare operators and prospective carshare communities should carefully consider hub locations (which can affect usage rates), the number of vehicles per hub, and the expected demand over time.

Since the 1970s, stakeholders have expressed concerns about the ability of transportation travel demand used by metropolitan planning organizations to represent induced travel from expanded highway capacity. Failure to adequately represent induced travel will underestimate vehicle miles traveled and congestion when comparing scenarios with and without highway capacity expansion. To examine the magnitude of potential biases, the authors use the state-of-the-practice transportation demand model, the Sacramento Council of Governments (SACOG) SACSIM19 model, to examine (1) the model's representation of induced travel, (2) the influence of variation in key inputs on vehicle travel and roadway congestions, and (3) the effect of changes in induced travel-related input variables on the comparisons of scenarios with and without highway expansions.

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The Caltrans 2024 Sustainable Freight Academy was held on November 18-21, 2024. The academy consisted of presentations from goods movement professionals and subject matter experts, including those from both public and private organizations. The final group presentation allowed participants to develop their skills in grant writing by applying lessons learned from the course. Participants were divided into eight groups and took on various roles such as Grant Writer, Project Manager, and Industry Partner in order to develop and present a mock Trade Corridor Enhancement Program (TCEP) proposal topic.

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The aviation sector in California is facing increased pressure to reduce its carbon footprint, leading to a growing interest in alternative fuel aviation (AFA) technologies such as sustainable aviation fuel (SAF), as well as electric- and hydrogen- powered aircraft. The report develops a California Aviation Energy Model (CAVEM), examining various AFA technologies and analyzing possible policy options. The analysis emphasizes the importance of SAF in the short term, with projections indicating sufficient supply for intrastate flights and capped vegetable oil-based fuel consumption. Long-term efforts are focused on electric and hydrogen-powered aircraft, which remain in the early stages of development. Electrification of intrastate flights is deemed feasible, with estimated electricity consumption amounting to a small percentage of overall electricity generation. The report highlights the necessity for additional policy incentives (such as tax exemptions) and a comprehensive policy framework to effectively promote sustainable aviation in the long run.

While the United States has long supported basic needs of residents through social welfare programs, policies supporting affordable transportation for lower income individuals have been much more limited. Federal support for transportation includes subsidies to transit agencies and requirements to offer discounted fares to certain groups such as seniors and riders with disabilities, but income-qualified discounts are not required. This study explores opportunities for improving access to transportation affordable programs by gathering insights from existing income qualified transportation benefits. Researchers compare examples of these programs to design features of existing non-transportation benefits to characterize opportunities for increased coordination and standardization. Finally, as the U.S. has seen an increase in recent years of Universal Basic Mobility (UBM) pilots that provide flexible transportation funds, the study incorporates insights from UBM evaluations to understand how UBM design features may be useful to agencies who are pursuing transportation affordable discounts and subsidies. The results suggest that there is significant potential for income-qualified transportation program enrollment both for agencies that do not currently offer these benefits and for agencies that already offer them, and that inter-organizational coordination among stakeholders may be essential in implementing successful transportation affordable discounts or subsidies. Additionally, the structure of income-qualified transportation benefits may vary depending on agency resources. Finally, with transportation equity as growing priority for California and its transit agencies, program administrators may opt for programs with easy access and enrollment rather than those that create barriers to participation through strenuous application and verification procedures. 

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California's Zero Emission Vehicle (ZEV) mandate targets all new Light Duty Vehicle (LDV) sales to be ZEVs by 2035. However, the current charging infrastructure is not well-developed in California, primarily serving households with home charging setups and leaving a noticeable gap in public charging facilities. This gap is seen as a significant barrier to Battery Electric Vehicle (BEV) adoption within California. This report explores driver charging behavior and their preference for public DC fast charging (DCFC), drawing on Stated Preference (SP) choice experiment data from a survey of 1,102 Plug-in Electric Vehicle (PEV) owners across California.

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International second-hand vehicle (SHV) exports are a multi-billion-dollar market for the US and an integral process in removing older vehicles from the road and enabling a robust new vehicle market. Mexico is the largest importer of SHVs from the US. As the US rapidly increases electric vehicle (EV) sales to meet decarbonization targets for the transportation sector, EVs will be an increasing large fraction of SHVs. While the benefits of EV adoption are numerous, introducing a radically new technology such as EVs without responsive measures in second-hand market regions may lead to an unintended transfer of economic and environmental burdens, especially if waste EV batteries cannot be managed properly. This research undertook a battery material flow analysis, life cycle assessment of SHVs traded from the US to Mexico, and a qualitive analysis of environmental and transport justice implications of SHV trade. The research finds that SHVs disproportionately contribute to waste battery generation in Mexico, and that second-hand EVs are frequently retired early due to a lack of repairability. In terms of life cycle emissions, SH EVs still contribute to reduced GHG emissions and air pollution relative to internal combustion engine vehicles newly sold in Mexico, but at end-of-life, their batteries are being disposed of in landfills, rather than in recycling facilities. From a justice standpoint, coordination between the US and Mexico and anticipatory policies are needed to ensure that only EVs with sufficient remaining battery life are transferred between the US and Mexico, and that sufficient infrastructure exists to safely dispose of waste EV batteries in Mexico.

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The goal of this study was to develop a framework and first order estimate of the greenhouse gas (GHG) emissions from the build-out and maintenance and rehabilitation of the world’s roadway infrastructure networks from 2020 to 2050. The GHG emissions from road pavement emissions, bridges, and maintenance and rehabilitation were calculated by decade based on the existing road networks and the modelling of their expansion. For comparison, the GHG emissions from vehicle manufacture and operation were estimated. Regional comparisons and sensitivity analyses were then performed. Based on one mid-range scenario, GHG emissions from new road construction account for roughly 0.1 to 4% of regional road transportation GHG emissions depending on the region; existing road maintenance accounts for 0.32 to 3%; vehicle manufacturing for 4 to 13% of regional GHG emissions; vehicle operation accounts for 82% to 93% of regional GHG emissions; and road roughness is responsible for approximately 2% of the total system impacts.

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