Driverless Cars to Help Reduce Costs, Pollution: Study

If driverless taxis roaming our cities become a reality, they would not only help cut our expenses but would also greatly reduce emissions of greenhouse gases, says researchers, including one of an Indian-origin.

The per-mile greenhouse gas emissions of an electric vehicle deployed as a self-driving, or autonomous, taxi in 2030 would be 63 to 82 percent lower than a projected 2030 hybrid vehicle driven as a privately owned car and 90 percent lower than a 2014 gasoline-powered private vehicle, the researchers calculated.

The study was co-authored by Jeffery Greenblatt and Samveg Saxena from from Lawrence Berkeley National Laboratory (Berkeley Lab), a US Department of Energy National Laboratory Managed by the University of California.

"When we first started looking at autonomous vehicles, we found that, of all the variables we could consider, the use of autonomous vehicles as part of a shared transit system seemed to be the biggest lever that pointed to lower energy use per mile," said Greenblatt.

Almost half of the savings was attributable to "right-sizing," where the size of the taxi deployed is tailored to each trip's occupancy needs.

Many automakers and other companies are working on autonomous cars. Right-sizing is cost-effective for both the fleet owner and for passengers, and small one- and two-seat vehicles are being explored by researchers and companies.

To illustrate the concept, consider a single passenger with no luggage versus a party of four passengers with suitcases. The single passenger would require a much smaller taxi than the party of four, saving money for vehicle owners and passengers. Right-sizing, of course, assumes a fleet of taxis managed by a single entity.

"Most trips in the US are taken singly, meaning one- or two-seat cars would satisfy most trips," Greenblatt said.

"That gives us a factor of two savings, since smaller vehicles means reduced energy use and greenhouse gas emissions," Greenblatt added.

Another factor contributing to lower emissions for autonomous taxis is a cleaner electric grid. By 2030 power plants are expected to be using more renewable energy and emitting less pollution, meaning the greenhouse gas intensity of electricity would be lower.

The researchers also conducted an economic analysis to determine how cost-effective autonomous taxis would be. An autonomous taxi using today's technology would be cheaper than an ordinary taxi not simply due to its greater energy efficiency, but also due to the fact that no operator would be required.

By 2030, autonomous taxis could be far cheaper than their driven counterparts, researcheres said.

The results were published online in the journal Nature Climate Change.