LOS ANGELES -- Elon Musk, founder and CEO of The Boring Company, announced that the first tunnel of a proposed underground transportation network across Los Angeles County would open in December.

"The first tunnel is almost done," Musk tweeted on Sunday. "Opens Dec 10."

The transportation network will be launched on the evening of Dec. 10, and offer free rides for the public the next day at speeds up to 155 miles per hour (250 kilometers per hour), according to Musk, also CEO of US leading electric auto maker Tesla and private spaceflight company SpaceX.

"Loop is a high-speed underground public transportation system in which passengers are transported on autonomous electric skates traveling at 125-150 miles per hour. Electric skates will carry between 8 and 16 passengers (mass transit), or a single passenger vehicle," the infrastructure and tunnel construction company says on its website.

The electric skates are faster than conventional subway cars, and are autonomous vehicles. Loop is an "express" public transit system - through the use of a main artery with side tunnels for entry and exit. Passengers travel directly to their destinations without stopping, says the company.

Workers have been building the tunnel for more than a year. Large pods ran through tunnels from Long Beach to Los Angeles International Airport, all the way to Sherman Oaks.

In June, the company won a bid to build a high-speed transport connection from Chicago's O'Hare airport to the city's downtown area.

The project would cut the trip from Chicago downtown to the airport to 12 minutes from a typical 45 minutes on mass transit, and is expected to be operational within three years.