Taxis capable of driving without human interaction could play a significant role in reducing greenhouse gas emissions, a new study reveals.

Berkeley Lab researchers studied the amount of greenhouse gases given off by various forms of automobile. They found that driverless taxis could provide transportation while doing the least amount of damage to the environment.

The study revealed that by the year 2030, self-driving electric vehicles could produce between 63 and 82 percent fewer emissions than hybrid cars likely to be available at that time. This production would be 90 percent lower than a 2014 model gasoline-powered vehicle.

"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," Jeffery Greenblatt of Berkeley Lab said.

Roughly half of that benefit would be gained by utilizing the minimum sized taxi for the number of guests, a practice known as "rightsizing." Several companies are currently developing self-driving cars, including one- and two-seater vehicles. When just one or two people, carrying no luggage, need to make a journey, a taxi company could send out a small vehicle. When a family of four, with a bevy of suitcases, need to get somewhere, a larger cab could be sent to pick them up.

"Most trips in the U.S. are taken singly, meaning one- or two-seat cars would satisfy most trips. That gives us a factor of two savings, since smaller vehicles means reduced energy use and greenhouse gas emissions," Greenblatt stated in a press release.

By the year 2030, most power plants in the United States are expected to be using more renewable energy, and emitting fewer greenhouse gases, than such facilities today. This means the environmental impact of powering electric vehicles could be lower than it is in 2015.

Self-driving cars could also provide additional benefits over today's human-directed automobiles. Not only would they accelerate and brake more smoothly than cars driven by people, they could drive immediately behind each other. This would allow the vehicles to save energy by driving in the wake of the automobile in front of them, like birds flying in a "V" formation. These benefits were not included in the new study.

Researchers calculated that by the year 2030, electric vehicles will still cost more than gasoline-powered cars to own and operates, with normal driving of around 12,000 miles a year. However, taxis average between 40,000 and 50,000 miles each year. This would allow the lower driving cost of these vehicles to offset the higher sticker price, researchers concluded.

Analysis of how self-driven taxis could help reduce emissions of greenhouse gases was detailed in the journal Nature Climate Change.

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