HOW GREEN IS YOUR RIDE? `Environmentally friendly' means different things to different people.(News)

Byline: J.P. VETTRAINO

Some car folk have asserted, with a hint of sincerity, that the greenest car ever sold is the Rolls-Royce Silver Shadow. Of 38,000 Silver Shadow variants built between 1965 and 1980, some 90 percent are still registered and roadworthy.

By this measure of greenness, Aston Martins and Ferraris probably run a close second, though it's a safe bet that more of those have been wrecked. As counterpoint to these enduring automobiles, the National Automobile Dealers Association reports that 12 million cars and trucks were scrapped in the United States in 2006. "Scrapped'' in this context covers a range of possibilities, from systematically recycled to submerged in country ponds.

In a thoughtful debate on environmental impact, few will hold fast to the notion that a Silver Shadow is the greenest car. But the point is taken. With attention focused on sexy propulsion sources, considerations such as manufacturing, duty cycle and disposal get lost in the roar. Does anyone really know what the most ecologically friendly car is?

Science can only guide us, and often the science gets buried under hype from all corners with something to sell.

"There's been a sincere effort to give consumers a rationale for comparing the eco-performance of vehicles,'' says Shruti Vaidyanathan, principal vehicle analyst at the American Council for an Energy Efficient Economy (ACEEE). "There's also a lot of hard sell that isn't based on good policy or science, and there are gray areas in measuring eco-performance. The ends of the life cycle are among the biggest.''

Gasoline-electric hybrids-particularly the Toyota Prius-have quickly become poster children for various environmental advocates. But there's plenty of evidence that hybrids aren't the greenest vehicles to build. One European think tank recently suggested that hybrids and their marketing schemes are actually impediments to genuinely sustainable green automotive technologies.