Self-driving cars could do more than allow passengers to nap, read e-mails, or watch movies on the road. When used as taxis, scientists say, the type of robotic vehicles that Google and Uber are building could also cut greenhouse gas emissions—a lot.

An autonomous or self-driving electric cab in 2030 could emit up to 94 percent fewer emissions per mile than a conventional gasoline car of today, and it could be far cheaper than taxis with drivers, says a study Monday by researchers at the Lawrence Berkeley National Laboratory. Almost half the savings occur, because the taxi is “right-sized” for each trip.

"Most trips in the U.S. are taken singly, meaning one- or two-seat cars would satisfy most trips," author Jeffery