The Boring Company Measuring 1.4 miles (2.3 kilometers) long and 14 feet (4.3 meters) wide, the test tunnel winds its way underneath Hawthorne and is estimated to have cost $10 million. This, Boring notes, is a fraction of the cost of traditional tunneling. It exists as a research and development tunnel for Boring's aspirations of improving tunneling capabilities and creating new modes of public transport. The tunnel was originally designed to have the capability to transport vehicles on a pair of innovative electric skates that zip along at up to 150 mph (241 kph). However, that plan seems to have been given the kibosh for now, with Tesla vehicles that use "tracking wheels," rollers that flip out from underneath the front of the car and keep it within the tunnel's one-way lane. Shortly before Tuesday's event, Musk tweeted an image of a Tesla Model X, on track, inside the tunnel, later clarifying that any autonomous electric vehicle, not just a Tesla, could use the system and that it would cost around $200 to $300 to install. Tesla in @boringcompany tunnel with retractable wheel gear that turns a car into a rail-guided train & back again pic.twitter.com/3a6i0NoSmi