The rapid transit tunnel that Elon Musk’s Boring Company is digging beneath Los Angeles will open on December 10th, and free rides will be offered to the public the following night, Musk tweeted on Sunday evening.

The two-mile test tunnel underneath SpaceX’s headquarters in Hawthorne, California, is a proof of concept for an underground public transportation system, which aims to transport passengers and vehicles beneath congested roadways on autonomously driven electric platforms called “skates.” The skates will theoretically transport eight to 16 passengers, or one passenger vehicle, along magnetic rails at speeds of up to 155 mph (250 km/h), Musk tweeted.

In August, Musk shared a photo of a Tesla Model S in the same Hawthorne tunnel. (Questions were recently raised about whether the second tunnel proposed by Musk would be wide enough to accommodate the all-electric vehicle.)

In June, the company was selected to build a multibillion-dollar rapid transit link between downtown Chicago to O’Hare International Airport, though the project’s sub-$1 billion price tag has raised questions among tunneling experts. In August, the Boring Company said that it would build a second tunnel in LA to ferry Dodger fans between Los Feliz or East Hollywood and the ballpark in about four minutes for about $1.

Last year, Musk said he hopes to connect New York City to Washington, DC via an underground hyperloop and has received tacit approval for the project from the Trump administration. Of course, transportation experts question whether tunnels are really an answer to the quandary of traffic congestion and overcapacity, in addition to questioning Musk’s claims that he can dig tunnels faster and at a fraction of the cost of traditional boring technology.