CAFE standards may be easier to meet than previously thought

By Sam Sklar

Consumers might favor vehicles that accelerate a little slower, if the vehicles are also much more fuel conscious and greenhouse gas friendly. That is the conclusion of a study published in Environmental Science & Technology by researchers at Carnegie Mellon, UC-Berkeley, and University of Michigan. The research might also help transportation agencies manage local safety if cars were to accelerate more slowly.

The findings could be used as evidence to nudge auto manufacturers to think about trading off acceleration for higher fuel economy, which in turn helps these manufacturers comply with stringent Corporate Average Fuel Efficiency (CAFE) standards issued by the National Highway and Traffic Safety Administration and the Environmental Protection Agency. To comply with CAFE standards, an auto manufacturer has to ensure that its entire fleet of non-truck vehicles meets a minimum miles-per-gallon ratio (currently 54.5 mpg for model year 2025). For some auto manufacturers, this data might provide enough evidence to encourage a focus on tweaking how the car accelerates, rather than spending a sizable sum on research and development for a technological fix for fuel efficiency.

An auto manufacturer can then make informed decisions based on a deep data analysis. The researchers ran two models. One model predicted to what extent varying factors like acceleration and weight of the vehicle affected fuel consumption and cost. Another looked at a driver’s willingness to pay for a certain kind of car based on individual preferences. The models took into consideration the likelihood that a potential buyer would care about these things, and would make a purchasing decision based on them. The results leave auto manufacturers three choices for this specific design consideration:

  • First, the automaker might find it more profitable to sacrifice acceleration performance of its fleet in favor of costly technological installation.
  • Second, the automaker might find it more beneficial to combine fuel-saving technology with better acceleration fleet-wide, so it can sell more fuel-efficient cars that also boast impressive acceleration.
  • Third, the automaker might alter acceleration in some of its vehicles, but look to fuel-saving technology in other ones to balance the overall fleet goals.

An automaker’s final decision will depend on how it wants to position itself within a specific market sector for automobiles in combination with how much it is willing to spend on compliance. Either way, this research provides evidence necessary to justify a decrease in greenhouse gas emissions without sacrificing profitability.

This research might also have an additional positive, unintended consequence for local safety. If cars accelerate more slowly, there is less chance they will achieve a lethal speed on a local street. Local streets with frequent traffic controls or traffic calming elements might be safer for pedestrians, whose survival in a crash is dependent on how fast a car is moving at the moment of impact. There is an exponential relationship between how fast a car is going and a person’s chance of survival. Not only could the acceleration tradeoff be a boon for global health policy by reducing fleet-wide carbon emissions, it can also be a signal to local communities that it is safer for their seniors to cross the street and for their children to get to school in one piece.

Sam Sklar is a Program Associate at SSTI.