Musk initially announced plans to build "hyperloop" tunnels to allow travel at more than 600 mph using magnetic levitation and vacuum tubes.
Those plans have been largely abandoned in favor of putting regular Tesla cars in standard-pressure tunnels.
So far, the company has dug more than 10 miles of
tunnels in Las Vegas, about 4 miles of which are currently operational. The company eventually hopes to have a 68-mile underground network in Las Vegas capable of moving 90,000 passengers around in Tesla vehicles every hour.