The current tunnel stretches for two-miles in Hawthorne, California, and is acting as a "proof of concept" for larger projects.
Musk wants to build a tunnel across western Los Angeles and another between a Metro subway line and Dodger Stadium.
Musk, a space entrepreneur and electric-car pioneer, has pledged to complete the test tunnel by the end of the year.
The public could get a chance to take a test ride on the Boring Company's futuristic, high-speed, underground traffic shortcut as soon as December 11.
Elon Musk says he's planning to offer the public free rides through a tunnel he bored under a Los Angeles suburb to test a new type of transportation system.
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The tunnel starts in the SpaceX parking lot and then turns west under 120th Street.
Musk has a reputation for often missing his own timelines, which prompted someone on Twitter to ask if the December 10 date is "in real time or Elon time?"
By lowering the cost of building tunnels and providing a transit alternative to driving, the company would help alleviate city congestion and offer high-speed transportation options across the country.
"The first tunnel is nearly done", Musk said on his official Twitter account.
In addition to the testing tunnel and the East Coast route, the Boring Company lists an underground tunnel project in Chicago. Musk replied, "I think real".