US entrepreneur Elon Musk has outlined his vision for a tunnel network under Los Angeles and shown how it might work.
Mr Musk also told the Ted (Technology, Entertainment and Design) conference he planned fully autonomous journeys across the US by the end of the year.
He spoke about how he wanted solar-powered roof tiles to be standard on “every home” within 50 years.
And he explained why he is committed to sending a rocket to Mars.
In a wide-ranging conversation with Ted curator Chris Anderson, the founder of Tesla and Space X said that he was inspired to consider a tunnel system to alleviate congestion because he found being stuck in traffic “soul-destroying”.