What did we learn from Elon Musk's big reveal? 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. The BBC's Peter Bowes takes a test ride on Elon Musk's LA tunnel Getty Images It was almost a white knuckle ride. A bumpy two-minute journey in a modified Model X through a concrete tunnel with a blue neon light in the ceiling. We reached a speed of 49mph, although cars will eventually travel at up to 150mph. Elon Musk later explained that the bumpiness was due to problems with a paving machine and that it would be "as smooth as glass" eventually. The vehicle was modified by adding two alignment wheels to keep it stable at high speeds and prevent it from hitting the side of the tunnel. Mr Musk said the $200-$300 attachments could eventually be fixed to any fully autonomous electric vehicle, for use in the tunnel. They would not interfere with the vehicle's normal operation. "We used Tesla vehicles because I run Tesla. What I am going to do? Use someone else's car?" he asked, smiling. Traffic solution? Alana Semuels, of The Atlantic, told the BBC World Service that Mr Musk had yet to unveil the technology that would allow vehicles to travel at such high speeds through the system. "At first he said we're going have these tunnels and transport people in pods, now he's saying we're going to transport them in cars, so I'm not sure even he knows how it works," she said. Getty Images