Honda's Environmental Learning Center (Honda).

When it comes to building more environmentally friendly vehicles, American carmakers have made gains in the last few years, but three Asian carmakers again topped the "2010 Greenest Automaker" rankings. This list and accompanying report is produced semi-annually by the Union of Concerned Scientists (UCS), a nonprofit organization headquartered in Cambridge, Massachusetts.

In a "photo finish," Honda edged out Toyota and Hyundai, who tied for second place. This was the fifth time that Honda took top honors in the rankings, which the UCS has conducted since 1998. The new analysis is based on data from model year 2008, the most recent full year for which data was available, according to UCS.

Scoring Sales

Honda finished with an overall score of 86, reflecting a fleet that was 14 percent cleaner than that of the top eight manufacturers combined. Toyota and Hyundai each finished with 87. Volkswagen came in fourth place (90), followed by Nissan (93), Ford (108), General Motors (109) and Chrysler (113).

UCS's automaker-ranking analysis captures the carmakers' real-world environmental performance, based on the average per-mile emissions of the entire fleet of vehicles sold that year by that carmaker. The organization scored each of the top eight automakers (comprising 92 percent of model year 2008 U.S. sales) against the "industry average" of all eight combined. The methodology weighs both the fleet's smog and global warming scores equally to determine each automaker's overall score. With the industry average assigned a score of 100, automakers' scores reflect how far above or below average an automaker ranks in terms of polluting emissions. Lower scores are better and higher scores are worse.

"At one point, it looked like Toyota was poised to take the lead, but it later stalled in its efforts to reduce carbon emissions," said Jim Kliesch, a senior engineer in UCS's Clean Vehicles Program and the author of the rankings report. "Meanwhile, Hyundai's fleet saw dramatic efficiency improvements."

Domestics Disadvantaged

Some car buyers may be surprised by these rankings, given how much press some of the domestic carmakers have received recently for their "greener" cars, like the hybrid versions of the Chevy Malibu and Ford Fusion, and the plug-in hybrid Chevy Volt. "But, remember, we base our rankings on the carmakers' entire fleet, and many of these carmakers are still building and selling large pick-up trucks and crossovers and SUVs," said Kliesch. "So, the smog and global-warming emissions of those large vehicles definitely pull down the rankings of a carmaker that is, on the other hand, producing a lot of smaller, more environmentally-friendly vehicles."

The three Detroit automakers have regularly placed at the bottom of UCS's emissions rankings, in no small measure because they dominate the pickup truck market. Of the three, Ford has generally been the best, though this year only one point separates it from General Motors. "Ford is using the right playbook now by relying on both class-leading hybrids and better conventional technology. The company's future score will depend on how many of these vehicles get into consumers' hands," said Kliesch.

Consumers are the key to lowering emissions, says the UCS, which is why its rankings are based on real-world sales. "We base our rankings on the vehicles that are sold, and driven. So, in order for these more green vehicles to have an impact on the environment, consumers have to get on board and buy them," he said. "And, to that end, the carmakers need to devote sufficient marketing efforts to make consumers more aware of all of the benefits of driving a greener vehicle."

Changes Brewing?

Even though Honda has now captured the group's top ranking five times, it will need stronger sales of efficient hybrids and better environmental performance from its conventional vehicles to hold on to the spot next time around, the report concluded. Toyota also will need to make fleet-wide improvements to continue to be highly ranked. "Without its successful Prius hybrid, the company would have placed fourth this year instead of second," Kliesch said.

Today, 20 percent of global-warming emissions in the U.S. come light vehicles, which also produce one-sixth of the smog-forming gasses, Kliesch noted, adding that "the good news" is that carmakers have recently found more ways to decrease smog emissions.

All of the automakers have improved their performance since UCS first ranked them, and the gap between the worst and best automaker has narrowed as well. State and federal emissions laws, along with a growing market for clean cars, are prodding automakers to produce cleaner vehicles.

The Department of Transportation and Environmental Protection Agency have recently outlined intentions for the next round of clean car standards covering model years 2017 to 2025. UCS and other groups are pushing the agency to adopt an average fleet-wide standard of 60 miles per gallon and 143 grams per mile of global warming pollution by 2025.

"One of the analysis' clear findings is that clean car policies work," said Kliesch. "There's great ingenuity in the auto industry, and better products are already beginning to reach the market. In the coming years, stronger standards will guarantee that consumers reap these benefits."

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