Elon Musk has tweeted a new video of a tunnel constructed under a Los Angeles suburb to test a new type of transportation system.
Musk tweeted Saturday that he walked the length of the tunnel and commented that it is "disturbingly long."
The tunnel runs about 2 miles (3.2 kilometers) under the streets of Hawthorne, where Musk's SpaceX headquarters is located.
Musk envisions a transportation system in which vehicles or people pods are moved through tunnels on electrically powered platforms called skates.
He plans to show off the test tunnel with an opening party on Dec. 10 and offer free rides the next day.
Musk has proposed a tunnel across western Los Angeles and another between a subway line and Dodger Stadium.