With the federal government focusing more closely on ways to control greenhouse gases (GHGs) to combat global warming, some believe a complete overhaul of how transportation emissions are regulated in the U.S. is long overdue.

“You have to understand that transportation emission regulations when originally established back in the 1970s were focused on human health effects, not GHGs and global warming,” explained Noel Perry, principal of research firm Transport Fundamentals and senior consultant with FTR Associates.

“That’s why truckers have been the focus of so much emission regulation ahead of the other modes-- they operate the most frequently in close proximity to people,” he told FleetOwner. “Now, when you start talking about GHGs, emissions from all transportation sources – especially railroads – need to be governed much more closely.”

That’s one reason Perry questions whether initiatives to promote greater use of freight rail alone would actually result in a greener national freight transport system; that is, one expected to produce fewer GHGs. Rather, Perry contends that equalization of railroad and truck emission standards to control oxides of nitrogen (NOx), liberalizing truck size and weight rules, and making greater use of intermodal freight networks would do a better job of reducing GHGs emissions.

The key to reducing GHG emissions – of which carbon dioxide (CO2) is a major focus – boils down to improving the fuel efficiency of the entire transportation network, Allen Schaeffer, executive director of the Diesel Technology Forum, told FleetOwner.

“Reducing carbon emissions is a direct function of reducing GHGs,” said Schaeffer. “You do that by burning less petroleum fuel. But from a GHG perspective, you are no longer looking at controlling emissions from just a diesel engine by itself – you are looking at the fuel efficiency of the entire vehicle, which includes how it’s operated.”

In some ways, this is creating conflicting policies, Schaeffer noted. “We’ve spent the last two decades controlling particulate matter and NOx emissions in trucking, which led to reductions in fuel economy,” he pointed out. “Now, we’re looking to control GHGs, requiring improvements in fuel economy. If we’d started with this goal first, we wouldn’t have done what we did over the last 20 years.”

FTR’s Perry said that for optimal energy efficiency, one must look at the complete supply chain from start to finish, including the local pickup and delivery function at which trucks are far more efficient than rail.

“When all factors are considered, most freight currently moving by truck would consume more energy if converted to a 100% rail move,” he pointed out. “Instead, maximum energy efficiency might be gained from more transloading of freight between truck and rail, where truck is used for local transport and rail for the [long haul] movement. Government efforts should be directed at creation of more such truck/rail interchange terminals to make this option more accessible.”

Modifying existing truck size and weight standards – frozen for 20 years – would also aid in this fuel efficiency equation, noted Perry. “Traffic congestion has a direct correlation to fuel consumption and thus GHG emissions,” he said. “Allowing bigger trucks would translate into fewer trucks on the road, reducing congestion and thus GHG emissions.”

Finally, NOx emission regulations need to be harmonized between rail and trucking if GHG reductions are to be the main thrust of federal emission control policy. “One unit of NOx produces 310 times the global warming effect of one unit of CO2, the gas normally tracked in carbon comparisons,” said Perry.

“Because of differences in the regulation of truck and rail diesel engines, rail locomotives currently emit an average of 4.5 times more NOx per horsepower-hour than trucks. Further, when looking to the future, truck NOx regulations are tightened this year but they won’t be for rail until 2015. As a result, new locomotives today will still emit 6.5 times more NOx per horsepower hour than new trucks.”