Driverless vehicles could intensify car use, reducing or even eliminating promised energy savings and environmental benefits, a study led by a University of Leeds researcher has warned. 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, new research by scientists from the University of Leeds, University of Washington and Oak Ridge National Laboratory, published today in the journal Transportation Research Part A, says its actual impact may be complicated by how the technology changes our relationship with our cars.

Lead author Dr Zia Wadud, Associate Professor in the University of Leeds' Faculty of Engineering and a research group leader in the University's Institute for Transport Studies, said: "There is no doubt that vehicle automation offers several efficiency benefits, but if you can work, relax and even hold a meeting in your car that changes how you use it. That, in turn, may change the transport equation and the energy and environmental impact of road transport."

The study uses analysis of 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 US roads by 2050. 

It identifies several efficiency benefits of 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 (0% to 20% reduction in energy use) Improved traffic flow and reduced jams because of coordination between vehicles (0% to 4% reduction) "Platooning" of automated vehicles driving very close together to create aerodynamic savings (4% to 25% reduction) Reduced crash risks mean that cars can be lighter (5% to 23% reduction) Less emphasis from car buyers on high performance (5% to 23% reduction).