By 2030, electric-powered, self-driving taxis could produce one-20th the greenhouse-gas emissions (per mile) of the average car on the road today, according to a new scientific analysis.

Depending on how widely automated taxis are deployed, the shift could make a noticeable dent in total greenhouse-gas emissions, since transportation accounts for 13 percent of emissions worldwide today.

Two researchers from Lawrence Berkeley National Laboratory in California, Jeffery Greenblatt and Samveg Saxena, made the calculations in a study published in the journal Nature Climate Change today, concluding that automated taxis could produce per-mile emissions that are between 87 and 94 percent lower than those associated with the average car today. The amount of reduction depends on the potential variation in greenhouse-gas emissions associated with electricity in 2030.

The researchers' scenario does, however, depend on a certain important assumptions. They expect that self-driving taxis would most likely be electrified and that the cars would be redesigned to be much more compact and efficient, to account for the lack of a driver and the often low number of passengers on board.

Even so, the study offers another important new perspective on the likely impact that greater vehicle automation could swiftly bring. "By considering what happens when you're sharing, these vehicles enable much bigger energy savings," says Greenblatt. "I was surprised by how much cheaper a battery-powered electric car is to operate when you run it for 70,000 miles a year."