Your family is packed into the car; the kids are already asking when you'll be there. It's a long drive to the cabin and you've only just pulled out of the driveway. But then you swerve to avoid the neighbor's dog and bang... a flat. At the tire dealership, you find yourself facing a wall of apparently identical black rubber tires. Give me one with a good safety rating, you tell the salesman -- oh, and a long warranty (a good indicator of tread life). Done. Put it on the car already. We gotta get to the cabin before nightfall.

Automakers shop for tires too, when they equip their new cars, but safety and longevity aren't the only issues on their mind. They must also ensure that their vehicles' fuel-efficiency ratings comply with federal Corporate Average Fuel Economy, or CAFE, standards. One important way they accomplish this is by installing tires with low "rolling resistance." As a tire flexes and deforms to grip the road, energy is consumed (it's lost as heat). With low-rolling-resistance tires, more of the energy from the gas in your tank can be used to move the car forward.

Putting these tires on a Ford Focus, for example, can increase gas mileage by as much as two miles per gallon. The 160 million cars and light trucks on the road today collectively need 237 million replacement tires each year. If all of those cars had low-rolling-resistance tires, Americans could save up to 5.67 billion gallons of gas per year -- reducing our annual oil imports by as much as 4 percent. So why aren't we all using them?

According to Roland Hwang, a senior policy analyst at the Natural Resources Defense Council (NRDC), the problem is that few people even know that "green tires" are an option. There's no publicity, no standardized rating system, and therefore no consumer demand. What's needed, Hwang says, is a program like Energy Star, which uses federal funds to promote energy-efficient technologies for appliances such as refrigerators, lightbulbs, and washing machines. So far that hasn't happened with tires. "The federal government has failed to create a market to reward innovation," says Chris Calwell, an energy expert at Ecos Consulting.

Case in point: Michelin introduced the first energy-saving tires in 1992. Two years later, the National Highway Traffic Safety Administration proposed a system of rolling-resistance labeling, hoping to spur consumer demand. Ironically, however, Michelin's head start helped doom the idea. If federal standards had been adopted then, Michelin would have enjoyed a clear advantage, and that did not sit well with its competitors. Six other manufacturers, including Goodyear and Bridgestone/Firestone, mobilized to block the new labeling rule.

Michelin's competitors claimed that decreasing rolling resistance might compromise wet traction, an important safety concern. Independent experts dispute this. "That may happen if a manufacturer takes an existing tire line and tries to modify rolling resistance, but various technologies exist to design a tire with low rolling resistance and good wet traction from scratch," says Gene Peterson of the Consumers Union auto test facility. Peterson recently tested 22 replacement tires and found no direct relationship between rolling resistance and safety-related performance features such as braking.

There's no such thing as a perfect tire, of course, and according to Dan Zielinski of the Rubber Manufacturers Association, the real trade-off for low rolling resistance is more rapid tread wear. Peterson adds that the Consumers Union study found that tires with the lowest rolling resistance were not among the highest ranked in individual performance categories such as hydroplaning resistance, snow traction, and noise reduction. But much depends on the specific engineering of the tire and the uses to which it is put. For instance, a tire with good snow traction often has poorer dry-road traction, while one designed to maintain grip in off-road conditions may wear down faster when driven on regular roads.

Even if low-rolling-resistance tires have a shorter life span (and the jury is still out on that), Calwell insists they will result in long-term net savings in energy and resources, with any added cost to the consumer quickly offset by savings on gas. According to the tire manufacturer Pirelli, about 82 percent of the energy required for the manufacture, use, and disposal of a tire comes from gasoline -- the fuel needed simply to make the wheel go round. Fears that landfills will be overrun with energy-efficient but shorter-lasting tires are unfounded, Calwell says, because of the rapid growth of the recycling market. Today nearly 78 percent of waste tires find a second life as rubberized asphalt, highway noise barriers, flooring material, and other products or are used as an energy source in cement manufacturing.

New regulations in California may finally give green tires the attention they deserve. In October 2003, then Governor Gray Davis signed a bill into law requiring fuel efficiency labeling and ratings standards for all replacement tires sold in the state. (The regulations take effect in 2008.) Californians purchase 28 million replacement tires each year -- roughly 12 percent of the entire replacement market -- so even if only a quarter of these replacements are low-rolling-resistance tires, the California Energy Commission still expects annual savings of 77 million gallons of gasoline. The large market share of a state such as California has a way of spurring action at the national level. "As California goes, so goes the nation," says Hwang of NRDC. "It's only a matter of time before this gets adopted nationwide."
-- Laura Wright