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EPA Can Maximize Fuel Savings of Partially Automated Vehicles

June 30, 2021
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The term “autonomous vehicle” (AV) evokes the idea of fully self-driving cars that let humans completely disengage from the act of driving. But this ignores what is actually happening on the road today, where cars with some computer-controlled driving abilities are becoming commonplace. These vehicles have the potential to improve fuel economy, but that opportunity will depend on the actions of federal regulators, according to a new ACEEE white paper.

Our paper, Near-Term Impacts of Automated Vehicle Technologies, points to research showing that the partially automated cars on the road today—or likely to be developed and sold in the next 10 years—could have a wide range of possible impacts on individual vehicle fuel economy, either increasing it by up to 46% or actually decreasing it by up to 14%, compared to vehicles with purely human drivers. The paper investigates the near-term potential fuel economy impacts of automated vehicles, the gaps in the current federal fuel economy program’s treatment of these vehicles, and how the EPA might begin to fill in those gaps to guide the AV market toward better fuel efficiency.

Partially automated cars—those with cruise control (CC), adaptive cruise control (ACC), lane keeping assistance (LKA), and other features—are already a significant part of the market and continue to grow in both market share and complexity. Vehicles equipped with both ACC and LKA systems, which can function together, grew from 2% to 10% of new car sales from 2018 to 2019. In the first quarter of 2020, 26% of new cars delivered to dealerships were equipped with either ACC, where computers can control vehicle acceleration, or LKA, where computers can control vehicle steering, both under supervision and in limited traffic conditions. The fuel efficiency impacts of these partially automated vehicles are too large to continue to ignore.

Many drivers know that the way they drive can affect fuel economy. The same is true for computer-controlled and partially computer-controlled vehicles. The fuel economy impacts of ACC systems, for example, depend on the automakers’ design choices.

Yet AV technology’s impact on efficiency is not reflected in the fuel economy sticker that buyers see on the car, nor in the fuel economy standards that automakers must meet. Vehicle fuel economy is tested on dynamometers, essentially large treadmills, where vehicles must drive at preset speed cycles at all times. Automakers’ decisions about how their vehicles’ automated features change vehicle movement are excluded, by design, from the testing process. While there is an EPA program to reward automakers for fuel economy improvements that are not captured during the preset cycles on the dynamometer, such as more-efficient climate control systems, this “off-cycle” credit program is costly, time consuming for both automakers and the EPA, and not currently equipped to handle the coming growth in variety and complexity of automated vehicle systems.

To encourage automakers to design AVs that improve fuel efficiency, a good place to start is updating test protocols to detect and quantify such improvements. ACEEE’s new white paper recommends that EPA do the following:

  • Sort automated vehicle features into discrete groups based on capabilities. For example, systems that work only on freeways and combine both LKA and ACC would be treated the same.
  • Not allow AV features primarily designed to improve safety, such as automatic emergency braking, to earn off-cycle credits.
  • Design test protocols for each eligible group of AV features.
  • Design test protocols for features that are already market available or expected to be sold within 3 years.
  • Award credits based on how often AV features are actually used. EPA should estimate this value and use real-world data for AV features that have already been introduced into the market. These data and usage estimates should be updated regularly, and credits for future model years should be based upon the most recent data usage estimates.

These recommendations can be adapted into the off-cycle credit program without changes to required testing procedures. Therefore, over the short term, EPA should allow credits to be earned in this process on a voluntary basis. As the market for AVs grows, EPA should consider changing the required fuel economy testing procedures, mandate AV tests, and impose penalties for AV implementations found to decrease fuel economy.

If we fail to guide AVs toward better fuel efficiency, we may not only miss out on opportunities to increase fuel economy, but actually see fuel economy decrease, oil consumption increase, and air pollution worsen as a by-product of the deployment of AV technologies. These problems may be exacerbated by less direct impacts of vehicle automation, such as increased tolerance for long commutes or changes in traffic patterns, though such indirect impacts were beyond the scope of this paper.

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