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# Easy On The GasPUBLIC ACCESS

Research aims to make the land of the automobile run more efficiently.

[+] Author Notes

Executive Editor

Mechanical Engineering 128(07), 26-33 (Jul 01, 2006) (8 pages) doi:10.1115/1.2006-Jul-1

## Abstract

This article presents details of a research that aims to make automobile industry run more efficiently. In order to reduce mass, Toyota is looking for new, lighter materials to replace traditional ones of comparable strength. The National Renewable Energy Laboratory is studying techniques to reduce the fuel burned for air conditioning of automobiles, and getting help from a dummy that sweats. The lab's heat test dummy is called ADAM (from ‘advanced automotive manikin’), a one-of-a-kind creation built by Measurement Technology Northwest in Seattle to the laboratory's specifications. The manikin communicates with a finite element analysis model of the human body developed by the lab using software from Ansys in Canonsburg, Pennsylvania. The model predicts the body's response to its environment-skin temperatures, for instance, and other physiological information-and communicates it to the manikin, which can actually sweat. The National Renewable Energy Laboratory in Colorado is winding up its work in a research project to develop hybrid technologies for heavy vehicles, especially the ones that spend much of the time running short distances between stops to deliver packages, to bus passengers, or to pick up the trash.

## Article

Inside and out: The Toyota Camry hybrid, shown at left as it appears on the road, and to the right as it does under the hood, gets 40 mpg and has a sticker price about $1,500 higher than the highest-priced conventional Camry. In the United States, transportation almost always means the automobile. The economy, the entire fabric of society, is built around it. The family car made possible the regional mall, the subdivision in the suburbs, and the commute on the Interstate. Americans drive cars in order to reach public transportation. Of course, Americans aren't alone. People everywhere, if they can afford them., love cars. Decades ago, when the u.s. made its first contacts for Ping-Pong and tentative diplomacy with the People's Republic of China, Americans were fascinated by news clips showing the streets of Beijing filled with bicycles on the go. Now that the country is a manufacturing powerhouse, the bikes are giving way to cars. Right now in the States, we're going through one of those times of self-examination about our preferred way of getting around because fuel prices have spiked again. We read of families who have found their piece of the American dream, a home in the outlying suburbs, but they have a long drive to wor:k, perhaps a 60- or SO-mile round trip. At current prices, that can cost more than$10 a day for gasoline, at a time when bills for natural gas, electricity, and heating oil are also rising.

Lately, increasing numbers of people have been asking if it isn't time for a change.

But even at $3 a gallon, the incentive for change is not a matter of home economics. For a little more than$21 ,000-in the low-price range for a sport utility vehicle-a homeowner can buy a Prius and get 60 miles to the gallon. But anyone being frugal will take the Corolla, which starts at just over $14,000 and gets 30 mpg. Even with a tax credit of$3,000 to sweeten the Prius, that leaves a lot of money to pay for extra gas.

cool running

One of the considerations of the Partnership for a New Generation of Vehicles program was the cost of air conditioning and how to reduce it. The National Renewable Energy Laboratory is studying techniques to reduce the fuel burned for air conditioning of automobiles, and getting help from a dummy that sweats.

The lab, in Golden, Colo., estimates that power for air conditioning accounts for about 5.5 percent of the fuel consumed by light vehicles, or about 7 billion gallons a year.

According to John Rugh, task leader in the Vehicle Ancillary Loads Reduction program at the laboratory, "If the compressor power can be reduced 30 percent (not unreasonable), the national AlC fuel use would drop from 7 billion gallons to 4.5 billion gallons."

Congressman in sunglasses meets ADAM in NREl's thermal comfort lab, where a lamp shining on the windshield of the test vehicle simulates the sun.

Rugh said that preliminary calculations using test data from last summer suggest steps can be taken to permit a 30 percent reduction in air conditioning system capacity. That doesn't automatically mean a 30 percent drop in compressor power, but it could be near that, he pointed out.

The lab's heat test dummy is called ADAM (from "advanced automotive manikin"), a one-of-a-kind creation built by Measurement Technology Northwest in Seattle to the laboratory's specifications.

The manikin communicates with a finite element analysis model of the human body developed by the lab using software from Ansys in Canonsburg, Pa. The model predicts the body's response to its environment-skin temperatures, for instance, and other physiological information-and communicates it to the manikin, which can actually sweat. The manikin measures skin heat loss and transmits that information back to the FEA model, which calculates anew the change in physiological condition.

The FEA' model also transmits the skin temperature data to a thermal comfort model. As part of a project funded by NREL, researchers in the Center for the Built Environment at the University of Cal ifornia, Berkeley, put people through various thermal conditions and asked them to record their impressions of comfort or discomfort. The subjects' skin and body temperatures were recorded, too.

Among the discoveries that ADAM has made possible so far is that a ventilated car seat allowed for an estimated 7 to 7.5 percent reductiqn in the fuel consumed for air conditioning, with no loss of comfort.

The lab is also studying reductions of the thermal load in the cabin. Researchers have outfiUed a Cadillac STS with solar-reflective glass and paint, and a solar-powered ventilation system that will vent air when the vehicle's engine is turned off.

NREL ran tests of the system on the Cadillac last summer and will continue this summer, in a partnership of government agencies, industry, and the Society of Automotive Engineers. Test data so far show an average reduction of 7°C in cabin air temperatures and of 14°C on the dash. Rugh said thermal analysis shows that this much lowering of internal temperature could translate into a 25 to 35 percent reduction in fuel used for air conditioning.

The solar-reflective glass and solar-powered vent system are commercially available now, Rugh said.

The lab is also looking at using waste heat in a thermoacoustic cooling application, but according to Rugh, "That is long term and high risk at this point."

The reasons to save petroleum, the reasons that the federal government and many states are putting research money and tax credits into fuel-economy measures, are pohtical and social. T he risks of a largely impor ted fuel supply were discussed in an article published in this magazine last October. The authors were a former Secretary of State, George Shultz, and an ex-director of the C IA , James Woolsey. "Dependence," they said, " leaves us vulnerable."

California, the poster child of the car culture, has gone to great lengths to reduce tailpipe emissions. The state has tried to encourage automakers and residents to get more all-electric and hybrid electric cars on the road to curb the release into the air of unburned hydrocarbons and other emissions.

Research programs are developing highly efficient, non-polluting cars that run on hydrogen, maybe using fuel cells whose only exhaust is water vapor. The hydrogen will be drawn from various sources, we’re told, and will not be limited to fossil fuels that come increasingly from distant regions of the world.

Forces are at work, too, to promote alternative, renewable fuels, derived from maize or organic waste material. These technologies, it is said, will one day free us from reliance on dwindling commodities and will burn clean, too.

No one foresees commercial fuel cell cars filling the highways any time soon, although Honda says it plans to introduce one in three or four years. Alternative fuels will not replace gasoline without substantial investment from many sectors of the economy. And none of these technologies will come without its own complications.

Engineers are also working on ideas that may be available in the shorter term.

We talked to a number of people who are involved in automotive technology. They discussed various ideas for making cars more fuel-efficient—among them, reduction of rolling weight, more efficiency in hybrids, and cleaner diesels.

Reducing the rolling mass is something that any car buyer can do right now to reduce fuel costs: Simply go out and choose a smaller car. The alternative, combustion controls and the electronics to govern them, can be more expensive than the gasoline to be saved.

There are people who buy small, but as Paul William- sen of Toyota reminded us, far more people want a new car to be bigger, roomier, and more comfortable than the one they’re trading in. As cars become progressively bigger, reducing mass becomes problematical.

Williamsen is a Toyota product education manager. His job includes teaching dealership staff the ins and outs of the company’s cars.

“Do you have to have a 6,000-pound vehicle? Or can you get by with 3,000?” he said. “The biggest challenge is making cars lighter and still giving them the functionality our customers want.” High on the list of what customers want are safety, naturally, and room in the cabin.

A report, Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards, published under the auspices of the National Research Council in 2002, devotes a chapter to new and emerging technologies, from variable valve timing to continuously variable transmissions, that can enhance fuel economy. We found the text on the Web site of the National Academies Press, www.nap.edu.

According to the report, as much as 80 percent of the work of an engine in city driving is expended to overcome two properties that increase with mass—inertia and rolling resistance. Under highway conditions, however, relative mass has less influence on mileage.

Do you have to have a 6,000-pound vehicle? The biggest challenge is making cars lighter and still giving them the functionality our customers want."

## Mass Reduction

To reduce mass—or at least to curb the increase in mass as cars grow in size—Toyota is looking for new, lighter materials to replace traditional ones of comparable strength, Williamsen said. For example, there are many parts of a car interior, such as the dash, that consist of an upholstered surface over a hard substrate. At one time, the hard support would have been wood, and then later plastic. In some cases, Toyota has been able to substitute a material made of fast-growing grasses, which has a strength on par with composite wood and is lighter than wood or plastic.

One of the grasses, kenaf, is a plant of African origin that is cultivated in the United States for a variety of uses, for instance as a material for making paper without cutting trees. It can grow to a height of four meters in four to five months, and can yield two or three harvests a year in tropical climates.

How much you gain by using grasses is hard to say, but to play up the Earth-friendly angle of the material, Toyota has shown a concept car using kenaf fibers in the body, floor, and dash. But we’re not expecting to see that one on the road.

Automakers gained valuable insight into the use of high-strength lightweight materials during their work in the Partnership for a New Generation of Vehicles in the 1990s, according to Vernon P. Roan, a professor at the University of Florida. Roan, an ASME member, served on the committee of the National Research Council that reviewed the results of the Partnership’s work. He was vice chair of the committee toward the end of the project.

The Partnership for a New Generation of Vehicles is probably more widely known by its initials, PNGV. According to Roan, one of the project’s goals was to create automobiles that could triple the mileage of midsize sedans of the time, which was about TP mpg.

"To my knowledge, PNGV was first time we had a cooperative effort to develop precompetitive technologies."

The program considered a variety of power systems, including Stirling engines, fuel cells, and gas turbines. “At that point, we were still too far behind the curve on fuel cells even for a demonstration vehicle,” Roan said. “The only option to meet the time frame was to use a spark- ignition or diesel engine.”

In 2000, the Big Three automakers each came up with a diesel hybrid vehicle that got somewhere between 70 and 80 mpg. The automobiles met emissions standards at the time, but would fail new, tougher standards that were coming in 2004. They were concept cars that advanced the practical state of the art, although as products, the vehicles were not considered practical themselves.

None of the models was produced. In the committee’s report, there was no pricing information for General Motors’ model, the Precept. DaimlerChrysler’s vehicle, the Dodge ESX 3, was estimated to be $7,500 costlier than current premium cars. The Ford P2000 Prodigy was deemed “not affordable.” Roan pointed out that propulsion was not the project’s only consideration. Participants also studied other influences on fuel economy, including vehicle weight reduction, air conditioning, rolling resistance, and lubricants. The Partnership’s work led to advances in composites, and extended the use of aluminum and high-strength steel in automobiles, he said. GM measured best for drag coefficient times cross-sectional area, with 0.163. Chrysler came in at 0.22, while Ford was at 0.199. The Dodge had the lowest curb weight, 1,012 kg, and included many weight-saving composites. Roan said Ford innovated with aluminum and magnesium. Roan calls it a valuable program. “To my knowledge, that was the first time we had a cooperative effort among companies, government agencies, universities, and national laboratories to develop precompetitive technologies,” he said. The cooperation is continuing under the U.S. Council for Automotive Research, an organization funded by the Big Three and five energy companies to support non-competitive research. It is the umbrella under which GM, Ford, and DaimlerChrysler are participating in the PNGV’s successor program, the FreedomCar project of the Bush administration. Lightweight materials can lighten the auto body and maintain safety, but they force a change in manufacturing techniques and suppliers, which can be an expensive adjustment. Cars would cost more. Cars could be 40 to 50 percent lighter today, Roan said, but they would be too expensive to buy. If designs were to use materials that are moderately affordable, he said, “We’re looking for about a 15 percent weight reduction.” Even the more modest weight reduction would raise the prices of automobiles. David Foster, who was also on the National Research Council’s review committee, is a professor of mechanical engineering at the University of Wisconsin in Madison. Foster wrote us in an e-mail, “Reducing vehicle mass and the power-to-weight ratio are two big levers for reducing fuel consumption. The implications of this on our vehicle choices and our driving patterns is obvious. (To date it seems that the American consumer does not want to pursue this avenue.)” He pointed out that turbocharging can reduce mass because it gets the same power from a smaller engine. “The engine spends a larger portion of its operating cycle with less throttling and the mass of the engine for the given power is reduced, which reduces the mass of the vehicle,” he wrote. Foster, an ASME member, was supportive of the Partnership for a New Generation of Vehicles. “I think that this was a valuable endeavor, from which we will see technologies infiltrating into the market for years to come—albeit at a slow pace. I think that we are seeing some of the effects now. For example, variable valve actuation and cylinder deactivation were originally part of the PNGV portfolio of technologies.” Delphi Corp. markets a cylinder deactivation system that is available on a number of GM vehicles. The system, which shuts down some cylinders during periods of light load, can improve fuel economy by as much as 8 percent, Delphi said. According to Alan Falkowski, supervisor of V-engine engineering at the Chrysler Group, the 5.7-liter Hemi engine comes standard with a Multi-Displacement System, which turns off four cylinders when the power of a V8 isn’t necessary. Falkowski said it can increase fuel economy by 20 percent. Honda, meanwhile, is predicting that its cylinder deactivation system, which it calls variable cylinder management, will improve the efficiency of a V6 engine by as much as 11 percent. When the load on the V6 is light, the system shuts the valves of three cylinders, which then act as air springs until the extra power is needed. Over the past several months, Honda has issued statements about other fuel-economy initiatives. Takeo Fukui, president and CEO of Honda Motor Co. Ltd., announced at the North American International Auto Show in January that by 2008 the company will introduce a “four-cylinder internal combustion engine to improve fuel efficiency by up to 13 percent from 2005 levels.” The company has also said it will introduce, in the next few years, a diesel engine that will meet all emissions standards and will burn as clean as a gasoline engine. The company does not say how it will achieve these goals. ## The Return of Rudolph Diesel The diesel engine in general has been championed as a fuel-saving technology. But like the downsizing of cars to reduce weight, the diesel engine has met resistance among car buyers in the United States. According to the U.S. Environmental Protection Agency, after October 15 all diesel fuel sold for highway use must contain no more than 15 parts per million of sulfur. That is lower than the permissible limit for gasoline, which is 30 ppm. (Reductions for diesel fuel used in off-road equipment will come later.) The change in fuel will make selective catalytic reduction possible to remove nitrogen oxides from diesel exhaust. To this point, it hasn’t been practical because sulfur poisons the catalyst. Giorgio Rizzoni, director of the Center for Automotive Research at Ohio State University, pointed out that the diesel is Europe’s choice for fuel economy. But he cautioned, “The diesel will face a serious injection of technology to meet stricter emissions standards.” The favored emissions-control system in Europe is charged with urea. But that system involves a container the car owner must refill. The EPA, a spokesman said, is not keen on the idea of a system that relies on the owner to remember, or even bother, to fill another tank in the car. From FreedomCAR to your car the FreedomCAR and Fuel Partnership is a long-range operation. Government and industry are working out automotive and support technology based on hydrogen. The goal is to build up enough information so that automakers will be able to decide in 2015 whether or not to proceed with marketing hydrogen-fueled cars and trucks. The project, however, is already putting technology on the street. The industry's part in the project is handled through the United States Council for Automotive Research. USCAR is supported by the Big Three automakers—DaimlerChrysler Corp., Ford Motor Co., and General Motors Corp.—and five energy companies: BP America, Chevron Corp., ConocoPhillips, ExxonMobil Corp., and Shell Plydrogen (U.S.). The government's part is handled through the U.S. Department of Energy. USCAR was formed to conduct “precompetitive” research. That is, to collaborate on high-risk and long-range work to develop basic automotive technologies that the automakers can take and adapt for competitive products. The FreedomCAR project is addressing technical issues and attempting to establish that certain cost goals can be met. For instance, by 2010, it aims to establish that a fuel cell power system costing$45 per kilowatt can achieve a power density of 325 W/kg and 220 W per liter operating on hydrogen. Research is to bring that cost down to $30AW by 2015. There are also goals for hydrogen fuel delivery and storage, as well as an electric drivetrain—in short, the technologies needed to put hydrogen-fuel vehicles on the highway. One of the conditions for success is that the hydrogen era have the same mobility and diversity as our current gasoline age. It’s a tall order, but when we asked about it, USCAR said it is “optimistic that with continued government and industry support the goals of the program can be achieved.” According to USCAR, industry is already starting to adopt some FreedomCAR ideas, especially in the areas of materials and batteries. New composite material technology has been used in body panels by Ford and in pickup truck boxes by GM. DaimlerChrysler is using high-strength steels in different applications. Research also has enabled GM to develop and introduce a magnesium engine cradle in its Corvette Z06. Early work on warm forming of aluminum ultimately led to quick plastic forming technology and the production of parts such as decklids and liftgates, including those in the 2004 Chevrolet Malibu Maxx. Advances in nickel-metal hydride battery technology have been adopted by major suppliers and have wound up in all three domestic automakers’ electric and hybrid-electric vehicles. Examples include Ford's Escape and DaimlerChrysler’s minivans. USCAR research helped develop the foundational materials and architecture for the battery system that GM is using in the 2007 Saturn Vue Green Line Hybrid. USCAR’s activities, apart from FreedomCAR, include a new Aerodynamics Working Group, which is researching evaluation tools to help the automakers with design innovations. A Transmission Working Group is researching transmission improvements. Rizzoni tends to agree. “When you consider how many cars drive around with empty windshield washer fluid tanks, you know that’s not going to work,” he said. Rizzoni, an ASME member, is advisor to the Buckeye Bullet land speed racing team, a group of Ohio State students who designed and built the only electric-powered car so far to exceed 300 mph. When we spoke to him, Rizzoni had just returned from a trip to Europe that included a stop at the Swiss Federal Institute of Technology in Zurich, where he visited some of the people responsible for PAC-Car II. That is the competition car (subject of the Input Output feature in January) that got more than 12,000 mpg during the Shell Eco-Marathon. Rizzoni said an exhaust systems supplier is funding research at his center into an emissions-control system for diesels. “We’re looking at alternative ways to do SCR without urea,” he said. The project is studying a system that can extract species of hydrocarbons from diesel fuel and reform them into carbon monoxide and hydrogen. The synthesized gases are diverted to a catalytic unit in the exhaust train to convert NOx into less harmful gases, including pure nitrogen and water vapor. Diesel, or diesel-like, engines are under study at Sandia National Laboratories’ Combustion Research Facility in Livermore, Calif. One is called the homogeneous charge compression ignition, or HCCI, engine. It has been tested using gasoline, diesel fuel, and other distillates. It premixes fuel and air, as in a spark-ignition engine, but the mixture is compression ignited, as in a diesel. According to Dennis Siebers, the department manager for the engine combustion research program at Sandia, the system allows higher compression than a spark-ignition engine, avoids throttling losses, and has an efficiency “very close to current diesels.” Another experimental engine uses high levels of exhaust gas recirculation in a diesel and delayed ignition. In this case, delaying the ignition lets the fuel and air mix better, avoiding soot. The high EGR promotes cooler combustion—between 1,500 and 2,000 kelvin—compared with a conventional diesel, which can range from 2,200 to 2,600 K, Siebers said. NOx formation is considerably reduced in the lower range of temperatures. At present, it is hard to control combustion in the systems and the engines do not operate over the same broad range of loads that spark-ignition and conventional diesels handle. Siebers noted, though, that if the engines were adopted for hybrid electric vehicles, they would be called on to operate over a narrower range of loads than if they were used unassisted. Roan pointed out that diesels have a particular advantage over spark-ignition engines at low loads—that is, in local or city driving. The economy hybrids also shine in local driving. In some cases, they test better for mileage under local conditions. According to Toyota’s advertising, the Prius gets 60 mpg in town, and 51 on the highway. heavy-duty stop and go the National Renewable Energy Laboratory in Golden, Colo., is winding up its work in a research project to develop hybrid technologies for heavy vehicles, especially the ones that spend much of the time running short distances between stops to deliver packages, to bus passengers, or to pick up the trash. The Advanced Heavy Hybrid Propulsion Systems Program involves competitively awarded subcontracts to four manufacturers—Eaton Corp., Oshkosh Truck Corp., Caterpillar Inc., and Allison Transmission. The federal government’s budget for the four programs totals about$13 million, and manufacturers put up an equal amount of money.

Each company has a different focus. Eaton is building diesel- electric powertrains for package delivery trucks. About 20 trucks using the Eaton system have been in use for a couple of years. More recently, Federal Express, which has been using some of the early trucks, has ordered 75 more. Eaton has also announced an order from UPS for 50 trucks made by International Truck and Engine and Freightliner LLC that will use the Eaton drivetrain. The company is also taking steps to use the drivetrain in the bucket trucks used by utilities.

An Oshkosh representative said the company will be testing a prototype for a refuse truck this summer. (Another design for a hybrid refuse truck is discussed in this month’s Technology Focus; it stores energy in a hydraulic system developed by Parker Hannifin.)

Caterpillar, meanwhile, is working on a method of heat recovery that will use waste engine heat to generate electricity from solid state thermoelectric devices. The system will generate electricity for auxiliary power.

Allison’s interest is in applications for transit buses.

NREL will complete its role in most of the research projects by the end of this year. According to Bob Rehn, program director at the lab, NREL administered the funding, provided technical oversight, modeling, analysis, and help solving specific engineering problems, especially in the area of thermal management. It has also used its test facilities to test prototypes and measure emissions, to validate computer models.

More hybrids are on the way. Honda, for instance, has said it is developing a new dedicated hybrid vehicle for major auto markets around the world. The company expects to sell it in 2009 for less than the Civic Hybrid, which has a suggested retail price of $21,150. Falkowski said that in 2008 DaimlerChrysler will launch a hybrid Dodge Durango that will bring a 25 percent improvement in fuel economy in real- world driving conditions. He said the vehicle will “benefit the customer at highway speeds unlike current technology, which only works well in stop-and-go city driving.” In his remarks at the auto show last January, Takeo Fukui said that Honda expects to introduce a fuel cell car in the next three or four years. He said there is one already “in use by an individual customer in the real world,” and this fall the company will have “limited driving opportunities” with a prototype fuel cell car. ## Nothing For Free So what happens if some day we do run our cars on grain alcohol and gasoline pumps all over America grow rusty? James L. Sweeney thinks about questions like that for a living. He is a professor of management science and engineering and a Senior Fellow at the Stanford Institute for Economic Policy Research. Fie is also a Senior Fellow of the Hoover Institution. According to his biograpy on the Stanford Web site, “Sweeney analyzes economic and policy issues, especially those involving energy and the environment. He has particular interests in global climate change, automobile fuel efficiency, and electricity markets, including policy, economics, and technology strategies.” Much gasoline contains some ethanol, a fuel with a high octane number. Sweeney said there have been some air quality gains noted with E 85, a mix of 85 percent ethanol and 15 percent gasoline. Ethanol is primarily derived now from corn, and he reminded us, “We have other uses for that corn. We would potentially be squeezing food production.” Sweeney added that it takes energy to fertilize and grow corn, and also to distill it. Cellulosic ethanol, on the other hand, “has a wonderful promise, ’ he said. It does not use foods that human beings or livestock digest, but the technology to commercialize it doesn’t exist yet, and researchers are looking for an economical way to break down cellulose. Vernon Roan at the University of Florida brought up another point. He mentioned in passing that “plug-in hybrids look promising” as a means of decreasing fuel consumption. (A movement to promote this kind of hybrid car, which relies on electricity more than current models do, is examined in the feature “Juiced Up," which appears on page 34.) Suppose, Roan suggested, that we got to a point where gasoline sales actually declined substantially. Gold medal for being green: The 2006 Honda Civic Hybrid was named 2006 World Green Car by a jury of 46 automotive journalists during a ceremony at the New York International Auto Show this spring. The loss of gasoline sales reduces tax money needed to maintain roads. The governmept must turn somewhere to recover the lost revenue. "If the tax lost on gas were restored on electricity," Roan said, "then electrical power would lose some of its price advantage." And the roads cost money-and lots of it. According to the U.S. Census Bureau, state and local governments spent more than$65 billion for capital improvements of highways in the fiscal year that, for most jurisdictions, ended in the middle of 2004. That covered new construction and major repairs. With routine maintenance , thrown in, the total topped $118 billion. Meanwhile, according to the National Automobile DealersAssociation, total dealership sales of vehicles in calendar 2004 exceeded$714 billion.

A report from the American Public Transportation Association estimates that, for the same year, capital expenditures for all public transportation in the United States totaled \$13.2 billion.

Everything we do to improve our lives leaves our footprint on the world. Sometimes one of our footprints becomes a pothole. The question being raised now isn't one of stopping progress or of rolling back the clock. That would be pointless, even if it were possible.

But what more and more people are asking is this: How deep a footprint do we want to leave in the world where Our kids will have to walk?

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