Driverless cars may increase read reliance.

• Position: Automotive Automation

Development of autonomous driving systems has accelerated rapidly since the unveiling of Google's driverless car in 2012, and energy efficiency due to improved traffic flow has been touted as one of the technology's key advantages. However, research indicates that the actual impact may be complicated by how the technology changes our relationship with cars. If people can work, relax, and even hold meetings in their automobiles, they may drive more. That has the potential to erode the energy and environmental benefits of self-driving cars, researchers posit.

"There is a lot of hype around self-driving cars, much of it somewhat utopian in nature, but there are likely to be positives and negatives," says study coauthor Don MacKenzie, assistant professor of civil and environmental engineering at the University of Washington, Seattle. "By taking a clear-eyed view, we can design and implement policies to maximize the benefits and minimize the downsides of automated vehicles."

The study analyzes self-driving technology combined with data on car and truck use: driver licenses and vehicle running costs to model the impact on energy demand of various levels of automation on U.S. roads by 2050.

The analysis identifies several efficiency benefits from self-driving cars and predicts ranges of likely energy impacts, depending on the extent of adoption of the technology and other factors: more efficient computer-directed driving styles; improved traffic flow and reduced jams because of coordination among vehicles; "platooning" of automated vehicles driving very close together to create aerodynamic savings; reduced crash risks mean that cars can be lighter; and less emphasis from car buyers on high performance.

However, the study also predicts that the very attractiveness of self-driving technology could reduce or even outweigh the efficiency gains. It estimates a five percent to 60% increase in car energy consumption due to people choosing to use highly automated cars in situations where they previously would have taken alternative transportation, such as trains or planes.

"When you make a decision about...