Ratti said cars are now only being used about 5 percent of the time. Most of the time they are parked and using up valuable city space.

　　In the future, a self-driving car could give you a ride to work in the morning. But then the same car could be used throughout the day to take other people around the city. This car-sharing model would blur the lines between private and public transportation, Ratti said.

　　“We could potentially share cars and rides better. That means a city where you couldtheoretically make everybody’s destination in Washington or New York, or Singapore a big city or a small city with 20 percent of the cars we have today.”

　　He said another major change could be the removal of traffic intersections. “At that point, you could think about autonomous intersections. Intersections where vehicles don’t need to stop at a junction, but they can keep going and simply avoid bumping into each other.”

　　Ratti said he believes driverless technology will lead to more efficient and transportation. But it will also leave questions about who will truly benefit.

　　“When you think about building a shared infrastructure, the question is, who’s going to charge or bill other people? Who’s going to enact different transportation policies? So it really becomes much more about how we’re going to distribute the benefits of this new transportation system across society.”

　　Another big question is how ready the public is, or will be, to use driverless technology.

　　Researchers at Carnegie Mellon University in Pennsylvania are reporting positive results with self-driving vehicles.

　　Lead researcher, Professor Raj Rajkumar, said it really does not take long for people to trust the car enough to let go of the wheel.

　　“They begin to see that the vehicle is exact, very rational, drives safely, and then they begin to relax,” he said.

　　U.S.-based Local Motors has even used 3-D printing technology to produce self-driving vehicles. It recently introduced a new minibus called “Olli” that can carry up to 12 people.

　　The vehicle allows passengers to call for rides with a mobile app similar to Uber. The company says about 75 percent of the entire vehicle can currently be 3-D printed, and it can be fully assembled in 11 hours.

　　I’m Bryan Lynn.

　　And I'm Anne Ball.

　　Bryan Lynn reported this story for VOA Learning English. Additional information came from the Associated Press and VOANews.com. Hai Do was the editor.

　　We want to hear from you. Would you trust a self-driving car enough to take a ride? Write to us in the Comments section, and visit our Facebook page.

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　　Words in This Story

　　tractor-trailer n. large truck with a trailer attached to the back

　　disruption n. an interruption in normal progress

　　blur v. to make unclear or confused

　　theoretically adv. related to something that is possible, but not yet known to be true

　　sustainable adj. able to be maintained at a certain rate or level

　　rational adj. based on facts or reason and not emotions or feelings