For the typical American household, the single most environmentally impactful choice that can be made is to buy a more fuel efficient vehicle.1 In 2008, the average American household spent $2715 on gasoline and $1353 on electricity,2 and the transportation sector was responsible for the about same amount of greenhouse gas emissions as the electrical sector. (see Figure 1).
Caption: Figure 1: Breakdown of U.S. greenhouse gas emissions from energy, 2008.50 Transportation was responsible for 32% of these emissions, compared to electricity's 43%.
Whereas other household carbon- and energy-saving measures (such as eating less meat, switching light bulbs, or reusing shopping bags) require consumers to remember to and choose to change behavior repeatedly and/or in small ways (which has proved extremely challenging), the vehicle purchase decision happens once every few years. Therefore, policies to influence this consumer decision can have a higher impact on national sustainability, per individual decision, than those that seek to change other consumer decisions.
In the next several years, policy-makers have just such an opportunity with the arrival of the mainstream electrified, or plug-in vehicle coming simultaneously with the explosion of smart-phone enabled mobile information systems. It is technically feasible for a fully electrified vehicle using energy from 100 percent renewable resources to completely eliminate greenhouse gas emissions associated with personal vehicle fuel use (emissions would remain from land use impact of roads and sprawl, as well as the construction of wind or solar facilities, etc.). While such a technical potential is years in our future, the tools are at hand to begin rolling out electrified, plug-in vehicles that can save more than 50 percent of greenhouse gas emissions from fuel today. The availability of the plug-in vehicles in showrooms reflects many years of work and collaboration among the industrial, political, and environmental sectors. To ensure consumer acceptance and rapid scale up, however, more must be done, and mobile information systems can play a valuable part. These systems can not only enhance the success of plug-in vehicles, but also support a wider vision for sustainable transportation, which can be termed “Smart Transportation.”
This article outlines how smart, mobile information systems can bring cost-effective, low-carbon solutions to the transportation sector. Then, after outlining plug-in vehicle technologies and environmental impacts, we describe several specific ways in which mobile information can accelerate the success of plug-in vehicles. Finally, we show how mobile information systems and plug-in vehicles fit into a wider agenda for sustainable and smart transportation.
Lessons from the Smart Grid
Leaders in the government and in business have successfully rallied around the concept of the Smart Grid. According to the Department of Energy, the Smart Grid will apply “information-age technologies, such as microprocessors, communications, advanced computing, and information technologies”3 to improve our existing grid. The Smart Grid can, in the words of President Obama, “save us money, protect our power sources from blackout or attack, and deliver clean, alternative forms of energy to every corner of our nation.”4
We find that in the transportation sector, which puts a higher monthly fuel cost burden on American families than their monthly electrical bill, the same story can be told about the application of information technology (IT). Applying IT to transportation can replace opacity with real time feedback in topics ranging from traffic to fuel expenditures, and thus increase citizens', businesses', and policy-makers' ability to make more economically and environmentally responsible choices. The tools for such a Smart Transportation system are, literally, already at our fingertips and in our purses. One example is a Virtual Test Drive, which, as we lay out below, uses smart phones to educate citizens about the match between their driving habits and the potential cost, sustainability, and convenience advantages of different plug-in vehicles (See Table 1).
Smart Transportation Research and Technologies
Smart Transportation (and its cousin, Intelligent Transportation Systems or ITS) research has flourished in the past decade. Smart Transportation has many overlaps with ITS, including emphasis on the application of “advanced communications technologies into the transportation infrastructure and in vehicles.”5 But whereas ITS focuses on improvements to transportation safety, service, and efficiency, the term Smart Transportation encompasses a wider reach, including interactions between transportation and other components of life and energy use, as well as improvements to the transportation system.
The majority of research and funding interest in ITS centered on safety applications such as crash avoidance: If two cars know where the other is, they can override the driver in an emergency, and avoid hitting each other. Recently, an interest has emerged in the environmental implications of ITS. Most of this research focuses on better traffic management to reduce congestion and associated waste of fuel. For example, 1.6 percent of the fuel used in the United States (or 2.8 billion gallons) in 2007 was wasted as a result of traffic congestion, up from less than half a percent in 1982.6 Smart Transportation and ITS have been identified as some of the strongest solutions for this growing problem.7 For example, a study in New Mexico found that application of ITS technologies reduced traffic delays by 88 percent, by using techniques such as coordinated traffic signals and better monitoring.8
In addition, ITS research has expanded to make transit systems more convenient and useful, with the goal of driving up ridership and driving down more fuel-intensive personal vehicle use. The ITS research community has begun to look at ideas that can be implemented soon, even though there are many ITS ideas that cannot be truly implemented until every car on the road has the required technology.
Dozens of examples of implemented and applied smart technologies already exist. The most established example may be real-time feedback displays of fuel economy in vehicles, which can significantly improve fuel economy by altering behavior, as exemplified by the Toyota Prius display.9 Other examples of applied Smart Transportation include Progressive Insurance's “MyRate” program, which installs a telematic device in vehicles in order to refine insurance payments to reflect annual miles traveled and driving behavior.10 ZipCar and CityCar have smart-phone enabled vehicle reservation functions.11 NextBus sends data on bus arrivals to phones.12 GM's OnStar program helps with directions, vehicle maintenance, and emergency support using mobile communications technologies.13 GoLoco coordinates carpooling between friends.14 Finally, the Department of Transportation, other federal and state agencies, and private entities have deployed an ever-increasing number of traditional ITS programs, from on-ramp timing signals, to centrally controlled traffic lights, remote toll payment systems (such as EZPass, see Figure 2, and real-time traffic and weather feedback systems.15
Caption: Figure 2: A Smart Transportation technology: EZPass in New Jersey.
Ultimately, widespread use and cost-effectiveness of these information technology systems will be greatly expanded if they can leverage existing hardware, or if hardware can be built into the personal and transit vehicles where applicable.
Smart Transportation and Electrified Vehicles
Plug-in vehicles, including plug-in hybrid electric (PHEV), extended range electric vehicle (EREV), and pure battery electric vehicles (BEV), have become the next-generation vehicle of choice for U.S. policy-makers and automakers.16 See Table 1 and cited articles for more details about the differences between these and other plug-in vehicle technologies.17
While not abundant, efforts to unite these two important, forward-looking trends in transportation (plug-in vehicles and Smart Transportation) have started to emerge, with promising results. The California Department of Transportation commissioned a report on the synergies between ITS and hydrogen vehicles (which are similar to plug-in vehicles) in 2005, which found that synergies could exist, especially in using ITS to support refueling systems for alternative vehicles, as well as coordinating batteries so they could act as storage for the electrical grid.18 Abdul-Hak and Al-Holou found that plug-in vehicles could optimize energy management in the battery, thereby getting more miles per charge, with predictive knowledge about routes and driving patterns provided by ITS.19
Barriers to Plug-in Vehicles
Two major, education-based barriers confront the adoption of plug-in vehicles. First, citizens lack information about their current driving habits—information necessary to draw the baseline against which the alternatives can be compared. Specifically, drivers do not know their own daily and annual miles driven and fuel expenditures. 20 They are also confused about the implication of comparing one miles-per-gallon (mpg) statistic to another.21 Consumers also struggle with the relationship of the mpg “sticker” to real-world fuel economy.22 This lack of information impedes drivers' ability to make rational economic choices about vehicle purchases (for example, trading off higher upfront costs for improved fuel economy).23
Second, drivers do not yet understand the differences between conventional vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and battery electric vehicles. Several studies from academic and industry sources have found that familiarity with electrified vehicle technology, costs, and benefits is significantly lacking.24,25 One study found that stated “high” familiarity with all plug-ins was well under 20 percent, and for PHEVs under 10 percent. Furthermore, the study found that accurate understanding of the vehicles may be lower still than stated familiarity. 26 This confusion exists despite nationwide political and media interest. To begin with, comparisons of miles per gallon for conventional vehicles and miles per kilowatt-hour for BEV and PHEV vehicles are outside of the experience of virtually all users and, importantly, transportation policy-makers.
Further complicating the education landscape for those who want to sell an alternative type of vehicle is the fact that many consumers are not interested in strict economic rationality when purchasing vehicles: they value nonmonetary attributes more highly. 27 Accurate understanding of these attributes (such as environmental impact) is also undermined by the missing information identified above.
Some research and anecdotal evidence indicates that a multiday test drive is the most effective form of education, allowing users to experience for themselves how the battery wears down, and practice plugging and unplugging the vehicle.28 However, giving millions of such multiday test drives to users is not economically feasible.
Virtual Test Drive
The Virtual Test Drive (VTD) is a mobile device–enabled system that allows users to experience the benefits of a multiday test drive, without the expense. In this way, consumers can build enough knowledge to support a decision to purchase an plug-in vehicle. As described in Figure 3a, VTD highlights the ability of a Smart Transportation application to solve two of the problems described above: to inform drivers about their daily miles driven and fuel expenditures, and to provide a “virtual test drive” to educate them about plug-ins.
Caption: Figure 3a: Steps to use Virtual Electrified Vehicle Test Drive.
Recent studies have found that education can significantly increase consumer interest in purchasing an alternative vehicle by numbers ranging from 2 to 30 percent.29,30 In addition, education can “correct” interest from consumers who might be a bad match for a specific plug-in vehicle technology by 20 percent.31 These studies are important indicators, but more rigorous work is needed to better understand the relationship between education and purchasing.
The Virtual Test Drive has five steps, as shown in Figure 3a: (1) The driver either downloads the smart-phone application, or installs an off-the-shelf vehicle tracking device. (See displayed box to the right for more on these devices.) (2) The driver signs up via Web site, and links Web page to their device. (3) The device sends secure information about vehicle location, speed, and acceleration to a server. (4) The server turns this data into a “drive cycle,” which is then used to model how an electrified vehicle would have performed under the same driving conditions. The program has a roster of several different electrified vehicle options for users to explore, to which new vehicles can easily be added, and it can employ a variety of established modeling approaches that range from basic to highly sophisticated route tracking and modeling. 32 (5) The user signs into the Web site to see visualizations of (a) how far they drove that day, (b) how much they spent on fuel on a given day (or month) alongside how much they would have saved in an alternative vehicle, and (c) where a PHEV probably would switch into gasoline mode, and if/where a BEV would have run out of battery (see Figure 3b). In this way, VTD uses the characteristics of the Smart Grid—specifically modern, mobile IT and real-time feedback—to educate citizens and support more informed (though not necessarily more economically rational) decision-making on vehicle purchases in the future.
Caption: Figure 3b: Virtual Electrified Vehicle Test Drive educational interface. Users log data from their vehicles, then visit the Web site to learn about how they drive and get recommendations on what vehicles and techniques could reduce gasoline usage, saving money and pollution.
There are many ways to get smart-enabling data from individual vehicles to secure systems that can process the data for the benefit of individual drivers and system planners and operators. The major categories are:
In-vehicle mobile systems, installed by the manufacturer: These devices are installed in the vehicle before purchase. They can read data from the vehicle's on-board computer (including information about engine performance, maintenance, vehicle condition, airbag deployment, etc.). Their capability can be coupled with GPS and a cellular connection. The devices are used for navigation, safety (such as automatically calling emergency vehicles in the case of an airbag deployment), early maintenance warnings, etc. Examples include GM OnStar. The devices usually cost a small fee (as an option at purchase time) and also include a monthly cellular fee to maintain service.
After market on-board diagnostic devices: These devices can be purchased independently, and installed by plugging into the vehicle's on-board diagnostic port (usually near the left knee of the driver). The devices sometimes include GPS and cellular signaling technology. The devices are used to log data about engine performance and maintenance issues. Some insurance companies have begun to place them in cars to enable pay-per-mile insurance, as well as to develop rates based on safe driving characteristics. Many commercial fleet operators use these to track company cars' and drivers' performance and location. Devices can cost between $50 to $600 (depending on presence of cellular and GPS capabilities) as well as a monthly cellular service fee.
Smart phone apps: Most smart phones (such as the iPhone, Android, or Blackberry) contain GPS and accelerometer capabilities, allowing them to provide the locational services associated with the above devices. In addition, several devices exist that can plug into a vehicle's on-board diagnostic port and send a wireless signal to a smart phone. The smart phone then links the data with the relevant GPS coordinates and can send the data using the phone's existing cellular contract. Several apps have emerged for Smart Transportation using both the location/accelerometer features alone, or combining them with the wireless connection to the vehicle's computer. Apps cost anywhere from $0 to $20, and wireless on-board transmitters cost from $50 to $200.
Remote sensing devices: These devices sit in a vehicle and are logged when the vehicle passes close by a sensor. The most common example is EZPass or FasTrak devices that log when an individual car goes through a toll booth for automatic tolling. Devices cost little money and usually have no associated fees (beyond, of course, the tolls).
Environmental Impacts of Plug-in Vehicles
What would selling more EVs do for the climate? The answer depends on several factors, including the vehicle displaced by the EV, the environmental impact of the battery, and what type of generator makes the electricity. EVs reduce greenhouse gas emissions under every set of reasonable near term assumptions, and they always save oil. But the magnitude of savings is important to understand when deciding whether or not to buy (at a personal level) or support (at a political level) a plug-in. In general, plug-in vehicles save greenhouse gases in three ways:
In the vehicle, electricity can be converted to motion at about 80 percent efficiency. Gasoline can only be converted at 30–40 percent efficiency.
- It is more efficient to process and send electricity through wires than it is to process and ship/pipe gasoline.
- Some electricity is lower carbon (natural gas) or no carbon (wind or solar).
When studying the impact of any vehicle, it is important to consider the impact of driving the car, the impact of building the car and its components, and the impact of consequences of driving the car such as additional road construction or encouraging people to live far away from their work.33 Greenhouse gas impact, the focus of this section, is measured in carbon dioxide equivalents, or CO2-eq, with a time horizon of 100 years, using values recommended by the Intergovernmental Panel on Climate Change.34
We assume the process and related emissions needed to construct a conventional car, a hybrid, or an EV are the same, excluding the battery.35 EVs, however, have an additional environmental burden from lithium ion battery manufacture. The impact of the battery will vary depending on how big it is, what fuels are used to power its production (often a function of where the battery is manufactured), and if the battery comes from virgin or recycled material. We use an average of 120 kg CO2-eq per kilowatt hour (kWh) of energy capacity in the battery.36 Battery size in EVs will range from 5 kWh for hybrid applications to ~50 kWh for high performance battery electric vehicles.
Fuel and Operations
We consider vehicles powered by gasoline, electricity, or a mix of the two. Burning a gallon of gasoline creates about 9 kg of CO2-eq, while transporting and refining that gallon creates about 1.7 kg.37 With today's average U.S. generation mix, electricity creates about ~600 grams CO2-eq per kWh delivered to the plug, whereas in California, where the mix has lower carbon intensity (utilizing more hydro power and natural gas), each marginal kWh only creates ~330 grams of CO2-eq.38 If electricity came purely from coal (which it does not anywhere in the United States), it would create ~950 grams of CO2-eq. Electricity from renewable generation causes just over 0 grams, because manufacture of the wind turbines or solar panels must be taken into account.
Finally, we combine these assumptions to calculate the total lifetime greenhouse gas emissions from five different types of vehicles: an average U.S. car that gets 24 mpg, a car that gets 24 mpg of gasoline equivalent but runs on ethanol, a 50 mpg hybrid vehicle (that does not plug in), a plug-in hybrid vehicle with a 40-mile electric range, and a battery electric vehicle with a 100-mile electric range. We assume that the plug-in hybrid is in electric mode 80 percent of the time, and that the other 20 percent of the time, the car gets about 45 mpg. We modeled the PHEV and the EV under four electricity scenarios each: 100% coal, the 2010 average U.S. fuel mix, the 2010 fuel mix for California (which has a about half the greenhouse gas intensity as the United States), and 100 percent renewable fuels. As shown in Figure 4, the EVs always save greenhouse gas emissions compared to the average U.S. vehicle; fuel-use savings more than offset additional emissions from the battery manufacture. In addition, the CA and 100 percent renewable EVs have comparable or better emissions compared to the most advanced cellulosic ethanol vehicles (which are not yet commercially available). Data on carbon intensity for ethanol, both direct (combustion) and indirect (land impacts) emissions, as well as California electricity, were taken from the recently published Low Carbon Fuel Standard in California.39
Caption: Figure 4: Comparison of lifetime greenhouse gas emissions from different types of vehicles (~150,000 mile lifetime). EV greenhouse gas benefit depends on the comparison vehicle and the carbon content of the electricity it uses.
Figure 4 also indicates that (A) the displaced vehicle matters, and next to a hybrid the PHEV40 does not save many greenhouse gas emissions, and (B) using cleaner electricity (such as electricity in California) does impact the lifetime savings significantly. In the worst case scenario, using 100 percent coal for the electricity, the plug-in vehicles break even with a non-plug-in hybrid vehicle. The literature cited in the preceding paragraphs contains much more technical discussion of lifecycle impacts of various vehicle types, for those interested in other nuances.
Points A and B are critical when modeling the greenhouse gas savings of a large number of plug-in vehicles in the future.40 It is impossible to accurately predict how many plug-in vehicles will be on the road 10 years from now, because no mainstream vehicles have even hit the road, and policy, technology, and consumer reaction from drivers have yet to unfold (though this has not stopped plenty of groups from to make those predictions). We use a reasonable estimate based on a report written by the Electrification Coalition: five percent of the light duty vehicle fleet, or just over 11 million plug-in vehicles (half fully electric, half partially electric and partially gasoline), will be sold between 2011 and 2020.41
Figure 5 shows the greenhouse gas impacts of these vehicles under three scenarios. The medium case assumes that the plug-ins displace the average new car, which we pin to the Corporate Average Fuel Economy (CAFE) standard for each year; that carbon intensity of the U.S. grid decreases by 1 percent per year; and that plug-ins drive 80 percent on electricity. The high case assumes that the plug-ins displace cars 20 percent less efficient than CAFE, that the grid intensity decreases by 3 percent per year, and that plug-ins drive 90 percent on electricity. The low case assumes that the plug-ins displace vehicles that are 20 percent more efficient then CAFE, that grid intensity stays the same, and that plug-ins drive 70 percent on electricity. In all cases, we assume that one-third of the plug-in vehicles are sold in California. The high savings case also results in 80 million barrels of oil saved by 2020. We assume that sales stop for our fleet of 10 million after 2020, but that those vehicles continue to save greenhouse gas emissions until the end of their lifetimes.
Caption: Figure 5: Cumulative greenhouse gas emissions savings from a fleet of 11.2 million plug-in vehicles sold between 2010 and 2020 under three scenarios (5% of current fleet). Maximum cumulative savings are ~45 M metric tonnes of greenhouse gas emissions. In 2009, the U.S. emitted ~ 7000 M metric tons.
Smart Transportation can help push plug-in vehicles to the “high case”: With better information about routing and driver habits, the vehicles' computers can learn to optimize battery usage. In addition, Smart Transportation technologies and communications infrastructure could enable smart charging (having the vehicle charge at times that put minimal stress on the grid) or “vehicle to grid” often called V2G.42 In V2G, vehicles act as storage for the grid while they are parked, giving electricity back to the grid when it needs more, and filling up the battery the rest of the time. Smart charging and V2G can both help integrate variable renewables, such as wind, on to the grid, by toggling their charging patterns to match the rise and fall of the renewable resource.
We assumed that the road infrastructure and other upstream environmental costs are exactly the same for a gasoline vehicle and any plug-in vehicle. However, if plug-in vehicles cause people to buy cars who previously would have ridden transit or walked, or cause people to drive more miles per year because of lower operating costs, then this assumption would have to be revisited. It is more likely that individuals in nations that do not have fully mature automotive markets (like India or China) would fit the former case (lower operating cost for vehicles would cause more car ownership).
The latter case, often called the Jevons Paradox or rebound effect, reflects the worry that if driving becomes cheaper because of cheaper fuels like electricity (or less guilt-inducing, because of plug-in vehicles' lower carbon footprint), then people will react by driving more, thereby keeping the actual financial and greenhouse gas costs the same. The Jevons Paradox is named after William Stanley Jevons who, in 1865, wrote a book exploring the relationship of coal use and steam engine productivity. The Paradox is debated by economists, and most agree that the evidence is not strong enough to claim that all energy efficiency improvements “will increase energy consumption above what it would have been without those improvements,” though they also agree that it is a phenomenon that deserves more attention.43 Furthermore, in theory, vehicles may be a special case: While reducing the fuel cost per mile saves money, increasing the amount of driving per day may not actually increase the “useful work” done by the vehicle (most people do not want to spend more time in the car).44 This is different than, say, a steel production plant where it would be more useful to produce more steel for the same amount of money. However, savings on vehicle fuel could have indirect rebound effects, perhaps encouraging the owner to take a vacation to Hawaii, which is very energy intensive.45
Other studies have looked at data (as opposed to theoretical models). Schipper and Grubb found that in transportation, though the United States and Canada experienced significant increases in vehicle fuel economy between 1973 and 1995 (30 percent), drivers showed little change in activity, indicating that in these countries, very little rebound affect appears to have occurred.46 The rebound effect for transportation was lower than for other sectors (such as industrial efficiency or home electricity use). Other empirical studies have found similarly small increases in miles driven for U.S. drivers reacting to lower cost-per-mile of driving.47 Recently, one study suggested the rebound effect for personal vehicles declines substantially with increased income, and is therefore smaller today than in decades past, and likely to get smaller still as wealth in the United States continues to grow.48 Therefore, we assumed no rebound affect for our analysis, which is concerned with the United States. This assumption, like the assumption that plug-in vehicles will cause no current walkers/cyclists/transit riders to buy a car, would have to be revisited for other countries, especially lower income countries.
A Prescription for Policymakers
Plug-in vehicles can significantly reduce the environmental impact of personal vehicle use. Mobile information systems can, as shown by the examples above, increase the likelihood of success for plug-in vehicles and enhance their ability to save greenhouse gas emissions by avoiding stranding users who have run out battery, optimizing energy use in the vehicle by knowing where the vehicle is going on a given day, and other techniques described above. Certainly there are hurdles to Smart Transportation, including (like the Smart Grid) the challenges of implementing adequate privacy protection. And certainly more education will not cause all citizens to start to behave with textbook economic rationality with regard to vehicle purchases. Even taking these limitations into account, Smart Transportation will help drivers motivated primarily by economics to improve their budgeting, and help other drivers explore options that coincide with their values, such as environmental sustainability or convenience.
Implementing Smart Transportation can help save money and reduce oil use and greenhouse gas emissions by increasing the flow of information about transportation to consumers and policy-makers. It can also enable the penetration of new technologies, such as plug-in vehicles. Furthermore, it can support changes that are just as, if not more, important than plug-in vehicles: more carpooling, transit, and walking/biking. The United States can leverage existing infrastructure (smart phones) to “retrofit” existing cars, roads, and transit routes, and automakers have already started to build smart capabilities into new cars.
To enable Smart Transportation and its intersection with plug-in vehicles, federal, state, and local policy-makers should focus on several issues:
Supporting the build-out of an appropriate infrastructure to fuel new types of vehicles, and record data along roads. On charging infrastructure for refueling, it may be more important to streamline the process of installing charge stations than to subsidize the costs.49
- Supporting research and infrastructure that enable plug-in vehicles to drive as many miles as possible in “electric” mode, while keeping costs low. These include route planning and optimization, citizen education about plug-in vehicles, smart charging, and strategically located charging stations. All three enablers leverage Smart Transportation technologies, including telemetry and other communication of data.
- Making the grid as green as possible. Plug-in vehicles engaging in Smart Charging or V2G can support a greener grid, with appropriate advances in research, demonstration, and regulation.
- Helping automakers manufacture plug-in vehicles and components, through subsidies and encouraging more flexible, advanced manufacturing techniques.
- Not neglecting walk-ability, bike-ability, transit, and smart growth strategies for the sake of more efficient vehicles. Efficient vehicles are necessary to meet our greenhouse gas emission reduction goals for transportation, but they are not sufficient. Non–personal vehicle transportation warrants just as much research and policy support as plug-in vehicles, and it can also be enhanced by Smart Transportation technologies.
Implementing Smart Transportation can bring many of the same types of efficiency and advanced technology benefits as the Smart Grid. Transportation, which has a similar greenhouse gas burden and higher household financial burden on the United States than electricity, deserves the same attention as the Smart Grid. Plug-in vehicles, which hit mainstream showrooms early this winter, are an opportunity to realize a significant step towards transportation sustainability, and they demonstrate the potential benefits of Smart Transportation. The integration of mobile information and transportation to support plug-in vehicles is one important example of the wider potential of Smart Transportation to increase the sustainability of how goods and people move from place to place.
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25. McKinsey & Co., Exploring Electric Vehicle Adoption in New York City (PlaNYC) (The City of New York, January 2010).
26. Kurani and Axsen, note 24.
27. Turrentine and Kurani, note 20.
28. Lipman and Shaheen, note 18.
29. Synovate, “New Survey Shows Concern over Fuel Prices and Environment Drive Consideration of Hybrid Electric Vehicles to Highest Level Ever,” June 19, 2008, http://www.synovate.com.
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35. Chester and Horvath, note 33.
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37. Chester and Horvath, note 33.
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Laura Schewel is a graduate student in the Energy and Resources Group at the University of California-Berkeley, focusing on sustainable transportation. Previously, she worked on vehicle electrification and sustainable transportation at the Rocky Mountain Institute and was an Energy Innovations Analyst at the Federal Energy Regulatory Commission.
Daniel M. Kammen is the Class of 1935 Distinguished Professor of Energy in the Energy and Resources Group, founding director of the Renewable and Appropriate Energy Laboratory, and director of the Transportation Sustainability Research Center, both at the University of California–Berkeley. Kammen is also a professor in the Goldman School of Public Policy and in the Department of Nuclear Engineering at the University of California, Berkeley. The authors would like to acknowledge the Energy Foundation, the Karsten Family Foundation, and the Berkeley Fellowship for Graduate Study for their support. We thank Nate Holtman and Chris Jones for their help and comments.