Institute of Transportation Studies

Ambitious global goals to improve energy efficiency and reduce greenhouse gas emissions are motivating a shift to electric vehicles (EVs), which include battery-electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and fuel cell electric vehicles. In 2018, the governor of California called for five million EVs to be on California’s roads by 2030. The International Energy Agency projects a global increase in EVs from 2 million today to 280 million by 2040. Creating sustained market growth to meet such goals presents numerous challenges to all EV stakeholders, including governments, the automobile industry, electricity suppliers, non-governmental organizations, and consumers.

This policy brief summarizes the latest in a series of recurring surveys of consumers regarding their awareness and consideration of EVs. Two surveys of the population of car-owning households in California were conducted in February and June of 2017; sample sizes were 1,681 and 1,706, respectively. Several survey questions have been repeated over multiple years in similar samples, allowing comparison to earlier results.

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Driver behavior has a significant impact on vehicle fuel economy and emissions. Eco-driving refers to anything a driver can do to improve on-road fuel economy. The most common strategy used to promote eco-driving is an in-vehicle display that provides the driver with feedback about their fuel efficiency, typically in real-time.

This policy brief summarizes findings from an extensive review and analysis of many studies of eco-driving feedback conducted to determine the average impact of feedback on fuel economy and improve understanding of what types of feedback are most effective. The study provides the most accurate estimate to-date of the average impact of in-vehicle feedback on fuel economy and summarizes the current state of knowledge regarding characteristics of eco-driving feedback interventions that determine effectiveness.

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Ride-hailing services, which allow consumers to order and pay for rides through smart phone applications, have grown to a substantial proportion of the transportation market. Today, an estimated 15% of adults across the U.S. and 21% living in major U.S. cities have used ride-hailing services. The growth of ride-hailing services has raised questions about their overall effects on the transportation system. While they clearly offer a new form of mobility, there is concern they may increase congestion and air pollutant emissions. A limited number of studies have attempted to quanitfy changes associated with the increased use of ride hailing services.

UC Davis researchers examined how ride-hailing affects the total amount of driving (measured in vehicle miles traveled, VMT) as well as greenhouse gas (GHG) emissions. The researchers developed a framework of categories for analyzing the multiple aspects of transportation that may be affected by ride-hailing. These categories are: automobile ownership; number of vehicle trips generated; choice of mode of travel; empty (passenger-less) travel between drop-off and pick-up points, known as “network travel”; and destination choice and land use. Thirteen (13) studies were analyzed using this new framework: 8 used surveys of riders or recorded data on rider and driver activity; and 5 used simulated (“modeled”) travel in and around cities by automated taxis. By compiling multiple studies in the framework, stronger and more certain conclusions could be reached.

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Incentives for plug-in electric vehicles (PEVs) are typically designed to encourage broad consumer adoption of the new technology. However, maximizing the emissions benefits from electrifying the transportation sector also requires incentives targeted at stakeholders with high travel intensity, i.e., those with particularly high passenger occupancy and/or vehicle-miles traveled (VMT). This policy brief focuses on one such class of stakeholders: transportation network companies (TNCs) such as Uber and Lyft. It examines empirical data of electric vehicle use in TNCs and discusses research findings on the potential impacts of electrifying TNCs. It also raises important considerations for the development of future policy.

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Automated vehicles (AVs) may significantly disrupt our transportation system, with potentially profound environmental effects. This policy brief outlines the mechanisms by which AVs may affect the environment through influencing travel demand, as well as the magnitude of these effects on vehicle miles travelled (VMT) and greenhouse gas (GHG) emissions. Personal AVs and AV taxis (or ride-hailing services) are likely to increase VMT and GHG, exacerbate traffic congestion in city centers, and potentially lead to suburban sprawl. Electrification and vehicle sharing may reduce some of these environmental effects, but targeted policies must be put in place to ensure that these solutions are effective.

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Roads and highways act as barriers to wildlife. They disrupt movement of wildlife populations and connectivity between communities of interacting species. Transportation organizations and many wildlife agencies see highway crossing structures for wildlife as critical to mitigating highway barrier effects. These structures are optimistically assumed to be effective for most species, most of the time, but are seldom critically investigated.

Wildlife use of highway crossing structures can be highly variable and dependent on structural attributes, human use, and traffic conditions. Studies of animal behavior suggest that wildlife aversion to roadways—and possibly to crossing structures—could be related to traffic noise and light. If transportation organizations and wildlife agencies can confirm this effect they may be able to design more effective wildlife crossing structures and manage existing structures to increase their use by wildlife.

This policy brief discusses findings from research that measured traffic noise levels and used camera traps placed at 20 bridges and culverts in California that were known from previous work to pass at least one species.

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