Driving efficiencies associated with autonomous vehicles can offset the significant environmental impact of their sensing and computing subsystems in terms of energy consumption and carbon emissions.

A study conducted at the University of Michigan has concluded that savings from driving efficiencies in self driving vehicles can help reduce both lifetime energy use and associated greenhouse gas emissions by up to 9 per cent compared to conventional vehicles, helping maximise the environmental benefits.

Gregory Keoleian, director of the Center for Sustainable Systems at the University’s School for Environment and Sustainability, who co-authored the study, underlined the need to focus on energy efficiency when designing autonomous vehicles to help realise their full environmental benefits.

Also known as connected and automated vehicles or CAVs, these autonomous vehicles are typically equipped with multiple cameras, sonar, radar, LiDAR, a GPS navigation system, a computer and support structures. Researchers involved in the study examined the lifetime contributions of this on-board equipment to energy use and associated greenhouse gas emissions of the vehicle.

There were two types of CAVs used in the study – one powered by internal combustion engines and the other by battery – with the two vehicle types paired with sensing and computer subsystems of three sizes (small, medium and large) to create six scenarios.

The lifetime energy use and greenhouse gas emissions for each scenario from cradle to grave were calculated using the lifecycle assessment methodology.

An important finding was that the lifetime greenhouse gas emissions of battery-powered electric vehicles were lower by 40 per cent than vehicles powered by internal combustion engines, which was attributed to the inefficiencies involved in producing electricity from fuel combustion as well as higher fuel consumption resulting from the extra mass of the internal combustion engine.

The study’s lead author, Jim Gawron, a graduate student at the U-M School for Environment and Sustainability as well as the Ross School of Business, said the research proved that a battery-electric vehicle was a better platform for CAV components compared to the internal combustion engine vehicle in terms of minimising environmental impact.

On-board equipment such as sensing and computing subsystems in a CAV could increase its energy use and greenhouse gas emissions by 3 to 20 percent for reasons such as higher power consumption, weight and aerodynamic drag.

However, these environmental impacts are balanced by the operational benefits of autonomous vehicles including smoother, more efficient traffic flow.

The research was supported by grants from the Ford Motor Co.