The Tesla and SpaceX founder also donated $10 million to help fund global artificial intelligence safety research.

Elon Musk is a busy man: Tesla recently unveiled the all-wheel-drive Model S with auto pilot, SpaceX just crash-landed its Falcon 9 rocket, and the entrepreneur this week announced more plans for a trip to Mars.

So it's not surprising that Musk's plans for a $6 billion Hyperloop providing high-speed travel between U.S. cities has been put on the backburner.

Until Thursday, that is, when the businessman tweeted about a Hyperloop test track "for companies and student teams to test out their pods." The course will likely be developed somewhere in Texas.

"Also thinking of having an annual student Hyperloop pod racer competition, like Formula SAE," Musk wrote.

The Hyperloop made headlines in August, when Musk described a system whereby passengers would be transported at top speeds via tubes constructed above or below the ground.

Ideally, this Hyperloop could move 840 passengers per hour and connect cities fewer than 900 miles apartSan Francisco to Los Angeles, perhaps; or loops between Boston, New York, Philadelphia, and Washington, D.C. It would probably cost about $1.35 million per passenger capsule, or $6 billion in total, Musk said last year.

For more check out some early Hyperloop designs in the slideshow above, and see The Hyperloop: Another Great Transportation Failure?

While Hyperloop details are worked out, meanwhile, Musk is turning his attention to artificial intelligence.

The founder of Tesla and SpaceX has donated $10 million to the Future of Life Institute to run a global AI research program, backed by a long list of leading AI analysts, including the head of Facebook's AI Laboratory, Google researchers, and IBM Watson Group employees.

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Musk Tips Hyperloop Test Track in Texas