AMESBURY, MASS. — AT noon, Mark and Jamie Womble pull their 18-wheeler into the snowy lot behind Trader Alan's Truck Stop just off Interstate 95. Eight other trucks are here already, parked side by side. All have one thing in common: Even though this is a truck ''stop,'' their diesel engines are running.
The Wombles, a husband-and-wife driving team, will also stop - but not stop. While they eat lunch with the other drivers in the restaurant, their truck will idle outside, rumbling quietly in the freezing weather to keep the engine and fuel warm.
According to a report by the American Trucking Association, the hundreds of thousands of diesel trucks idling across the United States at truck stops are a major emissions problem.
Even though the Environmental Protection Agency (EPA) recently restricted the sulfur content of diesel fuel to cut pollution, tougher federal emissions restrictions may lie ahead if the trucking industry cannot curtail idling trucks.
With an estimated 1.28 million long-haul diesel trucks on American roads, the number of hours spent idling are in the billions. Truck stops are major stationary sources of carbon dioxide, nitrogen oxide, carbon dioxide, and volatile organic chemicals. Some 56 percent of all freight in the US is hauled by trucks.
According to Vic Suski, senior automotive engineer with the American Trucking Association (ATA), burning a gallon of diesel fuel at idle ''puts as much as 2.5 times the amount of ozone elements in the air as a gallon burned on the road.''
The average diesel truck covers 130,000 miles per year, spending 6,316 hours on the road, according to the ATA's Truck Maintenance Council. But it's only hauling freight for 3,095 hours - less than half that time. For 3,221 hours the truck is running but stopped, the engine rumbling at a low idle. About half that idling time occurs at truck stops, according to another estimate.
The problem is diesel-powered, but the solution may be electrical.
Community bears brunt
''The community surrounding the truck stop is bearing the burden of these emissions,'' says Steve Allen, a project manager for Energy Research Group in Boston, a consulting firm for energy issues.
Truckers, both independent owner-operators and fleet drivers, leave their engines idling for three main reasons: weather conditions, economic pressures, and old habits.
In cold weather, a truck's engine and fuel tank need to stay warm. Power is also needed for heaters, lights, and more in the living space just behind the driver where he or she spends the night, eats, reads, and watches TV. In the summer, cabs and perishable cargoes must be cooled.
''A lot of truckers are under the gun,'' Mr. Suski says. ''They have to make a drop [delivery], and if the engine won't start in the middle of winter, or anytime, they are finished.... The way to avoid that is let her idle.'' Jump-starting a diesel can cost around $100. Minor repairs may start at $300.
Despite truck manufacturers' assurances to the contrary, many drivers remain convinced that needless wear is caused when stopping and starting a diesel engine. Manufacturers recommend running the engine for five minutes to cool it down before shutting it off, but many drivers won't wait. They simply leave the engine idling while they eat, shower, or shop at a truck stop.
''There is no need to leave an engine idling except in cold weather,'' Mr. Allen says. ''Many drivers think it is good for the engine, and old habits are hard to break.''
So far only the Edison Electrical Institute (EEI) in Washington, D.C., has proposed what the trucking industry considers a possible solution: truck-stop electrification. Under this plan, truck stops would have outlets for ''electrified'' trucks to plug into upon arrival, the way trailer parks provide electricity for their clients.
For truckers, money saved
Built into the truck would be such off-the-shelf items as heaters for the engine and fuel tank, a heating/cooling device for the cab, and an automatic shutoff to kill the engine five minutes after stopping. Most of the components exist today, and it would cost between $1,500 and $2,000 to retrofit a truck with the equipment, according to Eric Blume of Electric Perspectives magazine. Truckers would pay for the electricity used.
''Idling costs a truck about $3,400 a year,'' says Mike McGrath, director of customer programs at EEI, while plugging in a truck would cost $1,369. ''We are promoting this plan strictly on the basis of economic benefits,'' he says.
EEI estimates the initial cost to a truck stop in the plan would be $1,500 per outlet, and the payback period between 8 and 16 months.
Truck-stop operators would earn about 76 cents an hour by selling electricity, even as sales of diesel fuel might decrease. The truck owner, particularly the owner-operator, would save more than $3,500 annually in fuel and lengthened engine life, according to an EEI estimate.
EEI calculates that one hour of idling time is equal to 80 highway miles of engine wear. With idling hours cut in half or more under the plan, engines would last longer.
A rough estimate of the annual emissions reduction under the plan is about 30 percent. ''Here is a chance to reduce pollution,'' Mr. Allen says, ''and at the same time to make money for truckers and truck-stop operators.''
EEI has formed an informal consortium including the EPA, the ATA, the National Association of Truck Stop Operators, and the Electric Power Research Institute to develop unanimity on the details of the plan. Pilot projects at several new truck stops would begin within two years. ''We're going to talk directly to drivers, too,'' Allen says.