Every day, millions of drivers from L.A. to Paris to Tokyo waste staggering amounts of energy going nowhere at all.

Stuck in traffic or waiting at stop lights, their engines churn away, consuming millions of gallons of fuel and spewing pollutants into the air unnecessarily.

Heavy trucks burn nearly 1 billion gallons (3.8 billion L) of diesel fuel annually while idling and emit 11 million tons (9.9 million t) of carbon dioxide, 180,000 tons (163,278 t) of oxides of nitrogen and 5,000 tons (4,535 t) of particulate matter, according to the U.S. Environmental Protection Agency.

Quantifying the waste generated by cars and light trucks is trickier business and, oddly, something the EPA doesn't track. On city streets, drivers sit idling 35% of the time, based on one estimate.

It doesn't have to be like this.

Hybrid-electric vehicles introduced Americans a decade ago to start-stop systems that shut down the engine while the vehicle is idling or decelerating.

In Europe, this common-sense approach is being rolled out steadily in new, low-priced vehicles, many of them propelled solely by internal combustion engines.

“We are seeing an increased level of interest now on start-stop,” says Sujit Jain, general manager-gasoline systems North America at Robert Bosch LLC.

“The driver is more clear now: carbon dioxide reduction, fuel-economy improvement and energy conservation,” Jain says. “It's the No.1 issue right now.”

As U.S. lawmakers ponder strict new corporate average fuel economy mandates, start-stop systems are among the solutions being considered to boost efficiency.

Based on the North American driving cycle, Jain says Bosch's start-stop system will boost fuel economy about 5%, as will converting a conventional gasoline engine to direct injection. Downsizing an engine's displacement and adding turbocharging is good for a 15% boost in mileage.

In the U.S., Jain says he expects the technology to arrive in full hybrid vehicles, as well as “micro-hybrids” — those with the ability to stop the engine at idle but without electric motors connected to the powertrain.

Bosch recently launched start-stop capability in Europe for the BMW 1-Series and 3-Series, as well as the Mini Cooper. Those micro-hybrids, however, are not slated for sale in the U.S., BMW says.

The German auto maker markets the technology as EfficientDynamics and says it can increase fuel efficiency about 17%.

Jain says the cost premium is minimal for a start-stop system, which requires a battery sensor, traditional crank sensor and alterations to strengthen the starter.

Valeo SA, a leader in the segment with its StARS micro-hyrbid system, estimates 0.5% of new vehicles in Europe come equipped with start-stop systems.

By 2012, however, the penetration rate in Europe is anticipated to reach more than 30%, in gasoline and diesel engines, says Dennis Laabs, Valeo North American research and development director.

Valeo says it expects 4 million micro-hybrids in Europe by 2010. In Europe, Valeo launched its StARS micro-hybrid system in 2004 on the Citroen C2 and C3 and later in the Smart Fortwo MHD.

StARS combines the alternator and starter functions and allows the engine to stop when the vehicle comes to a rest and to start immediately when the driver steps on the accelerator.

In highly congested areas, Valeo says StARS improves fuel economy up to 28% in fleet test drives, although the supplier says the gain in normal city driving is about 15%. Applied in the U.S. market, Valeo estimates start-stop technology could reduce CO2 emissions by at least 4 million tons (3.6 million t) annually.

General Motors Corp. and Ford Motor Co. have integrated start-stop systems in hybrid vehicles launched in the U.S. within the past three years.

In 2003, GM began offering its fullsize GMC Sierra and Chevy Silverado pickups with start-stop functionality, via an integrated starter/alternator damper supplied by Continental AG.

For a number of reasons, GM's micro-hybrid program ended in 2006 after selling only a few thousand units.

Although GM billed it as a bargain compared with full HEVs, consumers apparently considered the price premium of $2,500 too high for the fuel-economy gains.

Today, GM is launching new, sophisticated 2-mode HEVs, and all of them can shut off the engine at idle and during deceleration and steady-state cruising. By the end of 2008, GM says it will have eight full and mild hybrids on the road, all with start-stop capability.