Big Fuel Savings From Autonomous Vehicles

By 2050, connected autonomous vehicles could reduce fuel consumption by as much as 44 percent for passenger vehicles and 18 percent for trucks, according to a new study released by the Energy Information Administration.
However, those gains could be offset if autonomous vehicles make automobiles easier for everyone and and liberate shut-in populations, such as the elderly, disabled, and people too young to drive, the study says. By boosting the nation's total vehicle miles traveled, that scenario could slightly worsen fuel consumption.
"The largest influencer in potential fuel reduction … stems from vehicle and powertrain resizing," states the report, referring to a scenario in which people no longer need to purchase vehicles maximized for every potential use. Using a mobile phone, people could order a much smaller and lighter vehicle for a single-passenger office commute than the current situation, in which those same people might purchase a utility vehicle because it can manage an occasional hauling or camping trip.
Unlike some earlier assessments, in this "Study of the Potential Energy Consumption Impacts of Connected and Automated Vehicles" the consultants weigh the impact of electrification and shared use.
Autonomous vehicles enjoy a symbiosis with electric vehicles. They both employ wired, rather than mechanical, driving and braking controls. So manufacturers can eliminate the weight contributed by those mechanisms, producing more economical cars.
In other ways, too, it will make more economic sense for people to share vehicles than to own their own. The average owned vehicle sits idle 95 percent of the time, depreciating. A shared vehicle earns its keep by taking on other passengers. Insurance is expected to cost much less, because an estimated 94 percent of accidents are caused by human error, and those who don't own would bear a sliver of insurance costs.
The mobility-service companies that own the vehicles would have market incentives to reduce cost.
"This shift in ownership model would signify an important shift in personal mobility priorities, from performance and style to lowering the cost per mile to attract more customers with lower rates," the report states.
The report was conducted for EIA by the consulting firms Z, Inc. and Energetics Inc. and released in late March. The fuel savings are compared to a reference case—itself a projection of expected business-as-usual consumption. Like in-house EIA projections, the report surfs considerable uncertainty, especially beyond 2030.
Speaking in Chicago this month, the recent director of the EIA pointed out that EIA projections are less important than the variance the agency detects between different scenarios.
"How can you possibly have a forecast that's correct about 2050 or even 2040?" asked Adam Sieminski, who headed EIA from 2012 until January of this year. "The goal is to test how sensitive that endpoint is to changes in assumptions. The delta between scenarios is most interesting."
The delta between scenarios is much wider for driverless cars in this study than for trucks, which already tend to be sized for their tasks and have less potential to merge underserved populations onto the roadway. Truck companies are expected to favor autonomous vehicles because they spare them driver costs, and when trucking companies platoon those robot trucks they will also enjoy fuel savings.
"In one representative platooning test," the study says, "two semi-trucks trucks were platooned at a constant 64 mph at a 36-foot following distance. This configuration resulted in an average fuel consumption saving of 4.5% for the lead truck and 10% for the following truck."
All classes of autonomous trucks are expected to enjoy fuel savings that range from marginal improvements to about 18 percent.
Last year, Americans consumed 143.37 billion gallons of gasoline, according to EIA.