Entrepreneur Elon Musk has unveiled a prototype underground tunnel in Los Angeles which is designed to transport cars at high speed around the city.
The tunnel is only a mile (1.6km) long at the moment but the goal is a network to ease chronic traffic congestion.
Modified electric cars would be lowered into the tunnel and travel at speeds up to 150mph (240km/h), Mr Musk says.
The tunnel has been built by Mr Musk’s Boring Company, which boasts state-of-the-art engineering techniques.
Mr Musk, best known as the head of Tesla electric cars and the commercial SpaceX programme, arrived at the launch on Tuesday in a Tesla car modified to work on the “loop” system.
He was cheered by a small crowd as he emerged from the car at one end of the tunnel bathed in green and blue interior lights.