WASHINGTON—Decisions about locking in or revising fuel economy and emissions standards for the 2022-25 model years will be made by policy chiefs at the Environmental Protection Agency and National Highway Traffic Safety Administration, but teams of technocrats are working behind the scenes to provide the scientific evidence for how best to reduce pollution from light-duty vehicles.
Developing auto efficiency standards requires assessing the current state of technologies and projecting how much they will improve in coming years, along with associated costs.
Vehicles have become much more complex to analyze since 2010, so regulators say they are using large-scale simulations and benchmarking to improve their targets.
The EPA under President Obama set an overall target of 51.4 mpg for each auto maker's corporate fleet average, although the standard can shift based on the car/truck sales mix. That target translates to an average of about 36 mpg under real-world driving conditions.
Advanced technologies continue to proliferate, grow in capability and come down in cost, which is why the Obama EPA, in its waning days, said it determined that the next phase of fuel economy standards should be maintained after a minor downward correction. In fact, officials said the data showed auto makers could achieve tougher standards, but they opted not to raise them to provide investment and planning certainty to the industry.
More than 60 technologies were analyzed in the 2016 draft technical assessment, including smaller engines, advanced transmissions, improvements in aerodynamic drag, reduced mass, low rolling resistance tires, hybrid fuel cars and electric drivetrains.
The trick is to figure out how each technology works in combination with other types of equipment on vehicles, Dan Bogard, technology policy analyst at the Department of Transportation's Volpe National Transportation Systems Center, said at an SAE International conference in January.
And that task is getting more complex.
"When we started our analysis seven years ago, the world was much easier to model," said Michael Olechiw, a standards director in the EPA's Office of Transportation and Air Quality. "Midsize engines had an I-4 or V-6 option; it was port fuel-injected; it had a four- or five-speed transmission. Pickup trucks were equipped with V-8s and maybe V-6s."
"Now, that pickup might have a turbo downsized engine, a 10-speed transmission and might be competing against a vehicle with a diesel engine," Olechiw said. "So our tools need to be updated to reflect that."
Meanwhile, manufacturers are using technology for different applications than originally intended.
Technical experts, using publicly available data and industry-supplied methodologies, also are comparing vehicles of a similar size, shape and function to study their road load and how it can be improved.
Bogard said analysts must test assumptions about how much a technology can improve over time, how soon the technology will be available, how effective it will be when commercialized, product complexity and design constraints that limit how often a system can be redesigned, and consumer preferences for particular technologies.
"We think the changes we made to our modeling is responsive to stakeholder recommendations" and better aligns with NHTSA's model for calculating carbon emissions, Olechiw said.