Every day, millions of drivers from Los Angeles 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.

Idling 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’s SmartWay Transport Partnership.

Quantifying the waste generated by passenger 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, according to one supplier’s research.

Suffice to say the cost to the environment is high. It doesn’t have to be like this.

Hybrid-electric vehicles from Toyota Motor Corp. and Honda Motor Co. Ltd. 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 to conserving energy has taken hold and 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.

“They (auto makers) are talking about it much more now than they were a year ago,” Jain says. “The driver is more clear now: carbon dioxide reduction, fuel-economy improvement and energy conservation. In my mind, it’s the No.1 issue right now.”

As U.S. lawmakers ponder strict new corporate average fuel economy mandates to lessen reliance on foreign oil and curb pollution, suppliers are under intense pressure to help their OEM customers with affordable technology that allows vehicles to post significant efficiency gains.

Start-stop systems are among several solutions being considered, as well as downsizing engines, turbocharging, diesel combustion, cylinder deactivation and gasoline direct injection (GDI). Plug some of these pieces together, and the benefits can be sizable.

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

“So it adds up,” Jain says. “And frankly this is the bridge which will be needed if we are serious about the new CAFE requirement that is going to be rolling out here.” On the highway, however, start-stop systems offer no additional benefit.

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. “You will see that,” he says.

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 describes the cost premium as “minimal” for a start-stop system, which requires a battery sensor, traditional crank sensor and a few alterations to strengthen the starter.

“I know it is a very good value,” he says. “Otherwise, we would not see this reception from the customers.”

Valeo SA, a leading proponent of start-stop functionality 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% due to skyrocketing demand to improve efficiency for both gasoline and diesel engines, says Dennis Laabs, Valeo North American research and development director.

Valeo says it expects 4 million micro-hybrids on the road 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. The engine controller also must be modified to accommodate the system, but the alternator is unchanged.

A belt linking the system to the crankshaft restarts the engine. That same belt also can drive other accessories, such as the air-conditioning compressor, water pump or power steering.

“You are simply and transparently shutting off the engine when you do not need it,” Laabs says.

Installation is simple, and the system works with all gearboxes. Automatic transmissions, however, require an additional pump to maintain fluid pressure when the engine is stopped, Laabs says.

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.

At recent press events in Michigan, both Valeo and Bosch offered test drives in vehicles equipped with start-stop capability. Bosch hooked its system to an Audi A4, while Valeo installed its hardware on a GMC Envoy SUV.

Likewise, in a recent diesel technology tour of France, Valeo offered test drives in three vehicles with StARS: a Citroen C3, Smart Fortwo and a Volvo S40 diesel prototype.

All of the test vehicles driven in the U.S. and France performed as advertised. The engines shut down either during deceleration or when the vehicle came to a complete stop, depending on OEM preference.

For maximum fuel efficiency, the OEM can tune the system to shut down as quickly as possible and to restart only when the driver actually depresses the accelerator. Some systems are tuned to restart the engine once the driver takes his foot off the brake.

Despite years of advances and a decade in the marketplace, start-stop systems continue to function with a mild vibration and a burbling sound when the engine spins back to life. Operation is smoother and less noticeable than a decade ago, but the systems still have a way to go before they become completely seamless for the driver.

Valeo estimates StARS restarts the engine in less than 350 milliseconds.

For now, StARS is restricted to gasoline engines up to 2.0L in displacement and to diesel engines up to 1.6L in size. By 2009, however, the system will be able to accommodate any size gasoline or diesel mill, the supplier says.

Although the U.S. market appears more interested in full hybrids, Europe will continue pursuing micro-hybrids because they are cost effective, simple and easily integrated into production vehicles, Laabs says.

Japan has adopted mild and full hybrids but now is beginning to consider micro-hybrids, while the rest of Asia also is expressing interest in micro-hybrids, Laabs says.

Among U.S. auto makers, General Motors Corp. and Ford Motor Co. have shown significant interest in start-stop systems. Hybrid versions of the Ford Escape and Mercury Mariner cross/utility vehicles have offered the technology since 2004, and hybrid versions of the Ford Fusion and Mercury Milan sedans arrive later in 2008.

GM entered the gas-electric hybrid market in 2006, with the short-lived ’07 Saturn Vue Green Line, soon to be replaced by a mild hybrid version of the redesigned Vue. The Saturn Aura Hybrid also arrived in early 2007. All have start-stop capability as part of GM’s belt alternator/starter system.

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. Continental continues developing components for next-generation hybrids, including start-stop systems.

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

Even though 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, says Bill Rinna, manager-North American supply chain and technology forecast for CSM Worldwide in Northville, MI. Plus, marketing the technology was not a priority for GM, Rinna says.

But GM now is launching a new breed of sophisticated 2-mode hybrid-electric vehicles, and all of them have the ability to shut off the engine at idle and during deceleration and steady-state cruising.

When the driver needs more power, the gasoline engine springs back to life.

First out of the chute is the fullsize GMC Yukon Hybrid. GM also has announced plans for a plug-in hybrid version of the Vue.

During a recent test drive, the start-stop operation was extremely smooth, and the vehicle achieved 19 mpg (12.3 L/100 km), even when fully loaded, besting the fuel economy in a test drive of the much smaller V-6-powered Hyundai Tucson CUV, without start-stop.

By the end of 2008, GM says it will have eight full and mild hybrids on the road, all with start-stop capability.

tmurphy@wardsauto.com