Elon Musk said the Boring Company will show off its first tunnel on December 18, including 'modded but fully road legal autonomous transport cars'

The Boring Company's test tunnel near Los Angeles will open slightly behind schedule, but CEO Elon Musk said on Thursday that the launch would involve more than just a hole in the ground.

"Boring Company product launch on Dec 18. More than a tunnel opening. Will include modded but fully road legal autonomous transport cars & ground to tunnel car elevators," Musk tweeted.

In October, Musk tweeted that the Boring Company's first tunnel would be ready to use on December 10, but he did not mention that the transport cars and "ground to car" elevators would be revealed as well. It's unclear if the tunnel and the cars will be available for public usage, or if this will merely be a demonstration.

The tunnel revealed at the December 18th event will cover about 2 miles beginning near SpaceX headquarters in the Los Angeles suburb of Hawthorne. The company is also working on plans for a tunnel near Dodger Stadium, called the Dugout Loop, that would transport fans from nearby subways, directly to the stadium.

The company faced one of its first major setbacks this November after local groups sued the city of Los Angeles for exempting a Boring Company tunnel project from environmental regulations. The Boring Company subsequently agreed to withdraw its plans for that project, which would have consisted of a second 2-mile-long stretch, this time under western Los Angeles.

Read more: This picture of hellish LA traffic shows why we need a transportation revolution

For a company that "started out as a joke," Musk's tweet on Thursday makes his dream of a Los Angeles traffic-buster all the more likely to become a reality.