Emissions: Beyond 2010

The 2010 diesel engine emissions standards mark the end of a road first entered back in 1985 when the Environmental Protection Agency began to progressively ratchet down two harmful exhaust components: particulate matter (PM) and oxides of nitrogen (NOx). With the latest and last step in EPA's regulatory process, the two critical pollutants have reached levels so low that in many metropolitan areas

The 2010 diesel engine emissions standards mark the end of a road first entered back in 1985 when the Environmental Protection Agency began to progressively ratchet down two harmful exhaust components: particulate matter (PM) and oxides of nitrogen (NOx). With the latest and last step in EPA's regulatory process, the two “critical pollutants” have reached levels so low that in many metropolitan areas the air entering the engine is dirtier than the air coming out of the truck's exhaust. They are about as low as they can practically go.

Impressive, but that doesn't mean we've reached the end of truck emissions regulation, even if there are no new rules on the books — yet. Two months ago, a government panel of academic researchers and engineers released a long-awaited report laying out the next map for further modifying truck emissions. And in May, President Barack Obama pointedly threw his support behind the report, ordering both EPA and the Dept. of Transportation to create the rules that will turn those recommendations into reality.

While the two currently regulated “critical pollutants” impact air quality and related health issues, the new rules focus on two related areas with broader environmental and social effects: truck fuel economy and greenhouse gas (GHG) emissions. The two go hand in hand because burning carbon-based petroleum fuels creates carbon emissions, so improving vehicle fuel economy directly lowers an internal combustion engine's main GHG, carbon dioxide (CO2).

Scheduled to be phased in between 2014 and 2018, the truck rules are part of an overall energy strategy that looks to reduce U.S. dependency on foreign energy supplies and lower CO2 creation to address global warming concerns. Earlier this year, the federal government completed new standards for passenger vehicles that will require a gradual 30% decrease in carbon emissions and a 40% increase in fuel efficiency between 2012 and 2016. With the Administration publicly estimating that commercial trucks consume more than 2-million barrels of oil every day and account for 20% of transportation-related GHGs, no one was too surprised to see a truck mandate follow the automobile rules.

Unlike the car standards, the call for truck rules does not come with specific target numbers, but rather requires EPA, with the aid of the National Highway Transportation Safety Administration (NHTSA), to set standards based on research data. Much, if not all, of the guidance for determining the standards will come from the congressionally mandated report mentioned earlier. Created under the auspices of the National Research Council (NRC), “Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles” was put together by a 19-member panel that combined academic researchers, engineers and technologists with backgrounds in truck and component manufacturing, and even a retired director of maintenance for a major common carrier.


Like the current “critical pollutants” standards, the new emissions requirements will undoubtedly add significant cost to truck prices. Even without quantifiable standards determined yet, it's clear that dramatically decreasing carbon emissions by improving fuel economy will require extensive application of current and to-be-developed technologies that will all carry a price tag.

But the good news is that's where the similarity to current emissions regulations stops.

Reducing PM and NOx has increased truck complexity and initial cost while also increasing operational costs for truck users. In effect, fleets have borne the cost of cleaning up the air without receiving anything in return.

This time there's a payoff for fleets as well as society. For example, the report estimates that by 2020 combined technologies costing $84,600 could reduce a tractor-trailer combination's fuel consumption by 50%. That, they calculate, would only require diesel to be priced at $1.10/gal. to recoup the initial cost over a 10-year vehicle life. This “break-even fuel price” would be $2.70 for a refuse collection truck, which could see a 38% fuel improvement for a technology investment of $50,800, according to their numbers. Traveling fewer miles in a year, Class 6 van and utility bucket trucks would have substantially higher break-even fuel prices — $4.20 and $5.40, respectively — but also require substantially lower initial technology premiums.

In addition to the promise of a cost benefit for users, there's another significant difference from the current PM/NOx standards. The NRC panel has made it clear that EPA cannot rely on a one-size-fits-all rule like the fuel economy averages it's promulgated for cars with its CAFE standard. Instead, the group has told regulators that they must consider how to accommodate the widely varied applications of commercial vehicles. And that nod to the reality of fleet operations should result in more realistic emissions standards for all truck users.


Before EPA can set fuel consumption targets, it needs to figure out how to measure that consumption in a meaningful way. Most fleets track miles per gallon to judge fuel economy performance in their particular operation, but mpg “is not the appropriate measure for MHDVs [medium- and heavy-duty vehicles], since these vehicles are designed to carry loads in an efficient and timely manner,” according to the NRC report. “A partially loaded tractor-trailer would consume less fuel per mile than a fully loaded truck, but this would not be an accurate measure of the fuel efficiency of moving goods,” it points out.

The “most meaningful metric of fuel efficiency will be in relation to the work performed, such as fuel consumption per unit payload,” NRC says. While a ton-per-mile measure might work for linehaul trucks hauling freight, how do you measure fuel consumed by work performed for a refuse collection truck, or a utility service vehicle, or dozens of other application-specific operations using trucks?

For that reason, the report avoids recommending specific standard numbers or measurement metrics, instead instructing NHTSA “to establish standards tied to the task associated with a particular type of vehicle.” Not only do regulators need to consider different truck applications, but they also need “to determine if separate standards are required for different vehicles that have a common function.”

“I don't envy regulators in trying to put together [fuel-economy rules],” says Anthony Greszler, vice president-government and industry relations for Volvo Powertrain, the engine and component supplier for Volvo and Mack Trucks in North America. “If you standardize [on one measurement], you're going to drive technologies into situations where they won't work. So how many applications do you need to consider in a regulation, but not have so many that it's impractical? That's a tough task, and it has to be done carefully to deliver fuel efficiency but not drive high costs that don't deliver in certain applications.”

NHTSA “will have to define duty cycles well and then regulate by [vehicle] segment,” says Garrick Hu, one of the authors of the NRC report who has extensive experience in advanced engineering development with major truck manufacturers and component makers. “It's the only reasonable thing they can do. It won't be a simple metric like mpg, but it will somehow have to reflect efficient use of fuel.

“NHTSA will have to segment the market, construct a duty cycle for each, and then create a load-specific measure of fuel consumption — some measure of work achieved with that fuel in that duty cycle,” Hu says. “It might be ton-mi./gal for highway trucks, for example. Otherwise you'd end up with a half empty truck that gets better mpg but is less efficient in terms of work.”

Next Page: How To Get There


Once regulators solve the measurement problem and begin to set fuel consumption/GHG targets, the focus will move to achieving what are sure to be extremely challenging goals.

One of the fastest ways to improve overall fuel efficiency would be “to readdress truck size and weight limits,” says Hu. “We could do that immediately, but that's not a regulatory issue; it's a legislative issue, which makes it a political issue. The same with lowering speed limits. It would bring an immediate improvement in fuel efficiency, but that's legislated.” Or in other words, outside EPA and NHTSA's ability to change with regulation.

Meeting whatever targets are set by new regulation will most likely begin with simpler technologies that are currently available, but not widely used. Take the recommendations of EPA's SmartWay program for linehaul equipment, which are essentially low-rolling resistance tires and simple aerodynamic treatments for trailers.

“We know that low-rolling resistance and single ‘wide’ tires on both tractors and trailers improve fuel economy, but for a variety of reasons they're not utilized very often,” says Greszler. “And we've known for 30 years how to make trailers more aerodynamic. Those are the least technology-intense solutions that will have to be looked at as EPA moves to regulate complete vehicle efficiency.”

A multifaceted research program funded by the Dept. of Energy has also begun to reveal a likely path, or paths, to a 50% improvement in freight efficiency. Known commonly as the Super Truck program, it's actually a number of independent projects that pair up individual truck, trailer and component manufacturers to develop integrated approaches to vastly improve efficiency.

Navistar, Wabash and ArvinMeritor, for example, have received $37 million from DOE to build a Super Truck combination for linehaul work. “We start by viewing GHG emissions or fuel efficiency as an entire vehicle attribute,” says Ramin Younessi, Navistar's group vice president-product development and strategy. “Engine and powertrain efficiencies, aerodynamics, weight reduction, parasitic losses in bearings, brakes and tires — improvements in each will all add up.”

Daimler Trucks North America and its sister company Detroit Diesel Corp. are also working on a Super Truck project. On the engine side, it's looking at a wide range of approaches, including new fuel injection systems and controls, engine downsizing, improved turbochargers, electrified accessories, and ways to recover energy from waste heat. On the vehicle side, the research is focusing on complete combination aerodynamics, integrated engine/drivetrain systems, hybrid drivetrains, predictive technologies, idle reduction, and route planning.

“A 50% gain in efficiency is a very difficult target,” says David Kayes, DTNA's executive engineer. “We'll be studying some ‘stretch’ technologies that still require some [development] to become mainstream as well as technologies that are already more mainstream. The point [of the Super Truck project] is to achieve that target, but even if all these technologies might not work to get to that aggregate number, we want to learn what are the most pressing obstacles to cost-effective versions of these technologies. Then we can work to overcome those obstacles, and that will teach us how we can reach these goals in ways that make sense for our customers.”


The one advanced technology mentioned by everyone working on Super Truck projects or the NRC report is hybrid power. “The benefit of in-town hybrid use is obvious,” says Hu. All truck OEMs currently have diesel-electric hybrid systems that recover and store braking energy in stop-and-go applications, he points out.

“But hybrids also show great potential for on-highway,” Hu says. Using a hybrid powertrain could electrify a tractor's hotel systems to eliminate idling, as well as remove parasitic power losses from belt-driven accessories by electrifying them as well. “If the hybrid systems allow you to downsize the engine, then you can change the cooling system and reduce the frontal area for better aerodynamics. The overall package gains efficiency, maybe 10 to 20% in an over-the-road application.”

The real point isn't to look for a single silver-bullet technology to meet whatever fuel efficiency and GHG standards EPA eventually sets, according to Hu. “The market will drive the evolution of engine and component technology,” he says. “And hybrids need to be explored as more integrated parts of the powertrain. But the key will be having the ability to choose the appropriate technologies for each market segment.”

However those technologies develop, it's clear that the next phase in regulating truck emissions will focus on GHGs and will drive fuel efficiency to levels once thought to be impossible.

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