With public hearings being held this month regarding the Environmental Protection Agency's (EPA) proposal to tighten smog standards in the U.S., the trucking industry, which has already endured tighter regulations on diesel emissions, is waiting to see what impact the latest measure, if enacted, could have.

The impact may be minimal for the majority of the industry, experts said. Glen Kedzie, vp and environmental counsel, American Trucking Assns., said that given the useful lifecycle of a tractor, around 15 years, and the timeframe required to enact new regulations, the number of vehicles affected would be limited. “I don't envision it hitting us front and center; newer fleets won't be impacted,” he said. “Older fleets maybe,” depending on how long they hold onto their trucks.

EPA is proposing to set the “primary” ozone standard, which protects public health, at a level between 0.060 and 0.070 ppm measured over eight hours. This is a revision of a 2008 Bush Administration policy which set the level at 0.075 ppm. According to Kedzie, EPA would like to have a final rule in place by Aug. 31. The reduction to 0.060 ppm could double the number of counties that would be placed in a nonattainment zone. A final regulation closer to the 0.075 ppm would not affect as many counties.

Wherever the final regulation falls, trucking's path to reduce oxides of nitrogen (NOx) has it positioned well. With the implementation of emissions rules that went into effect Jan. 1, all engines being built now have reduced NOx emissions to 0.20 g/hp-hr. That is down significantly since 2002, when the levels were set at 2.5 g/hp-hr. “Because we have reduced our NOx levels to near zero, 0.2 grams, how can you say [to further] clean up the cleanest trucks in the world,” Kedzie asked.

According to Allen Schaeffer, executive director of the Diesel Technology Forum, the Clean Air Act requires a four-year lead time for manufacturers and three years of regulatory stability before any new engine emissions certification standards are issued. As a result, he added, the earliest new regulations could be enacted would be 2014.

Counties in nonattainment zones would work with states, who would submit plans to EPA on how the county would come into compliance with the regulation. Each county or state, Kedzie said, would have a different plan and transportation-related emissions are just one small factor in the makeup of smog.

For the states, “the timeline for being in compliance will vary based on how far out of compliance the state is,” Kedzie said. Some states may have 10 years or more to achieve compliance. In light of that, Kedzie said, the segments of trucking that would likely face new regulations as a result, such as retrofitting equipment, would be agricultural haulers, small fleets and owner-operators — the players in the industry who often purchase older equipment.

“Potential impact on this would likely come more from the state level and would be whether or not as part of its nonattainment plan a state would require retrofitting of existing diesel engines to lower NOx emissions on a more near-term basis — like the CARB rules, which some believe are ‘portable’ and could be adopted by other states in lieu of EPA federal requirements,” Schaeffer said. “I suspect that would be open to more legal interpretation before it happened. Because there is not much farther to go on the new engine side, I'd have to guess that if diesel engines are one of the targets to be made cleaner, then the existing fleet of vehicles offers more opportunity than new engines.”

Ultimately, Schaeffer added, is we don't know what impact this may have on the industry. Could retrofitting trucks be an option? Schaeffer couldn't rule it out. “Could new ozone standards spawn a market for SCR retrofits?” he asked. “Good question. [It] seems somehow far-fetched but also not so crazy since SCR could offer probably more NOx reductions to higher emitting older technology. … At the end of the day it would be better to have more trucks investing in 2010 generation technology for a wide variety of reasons rather than trying to upgrade a 2005 or 2006 model. ''