You may think that self-driving cars are mostly useful for reducing accident rates and freeing your time, but they might just help save the environment, too. Berkeley Lab researchers have published a study which suggests that switching the transportation grid from conventional vehicles to autonomous electric taxis would cut greenhouse gas emission levels up to 90 percent by 2030. While the clean EV powerplants would play a large part, the switch away from privately-owned cars that would make nearly as much of a difference. A big key would be "right-sizing" trips -- since you'd usually just need a tiny car to get around, you could avoid getting into a big vehicle until it's necessary. The base data doesn't even include some of the efficiencies that are inherent to robotic cars, like optimized routes and closely-packed traffic that cuts wind resistance.