Tesla Motors and SpaceX CEO Elon Musk is as well known for his companies as he is for unrealized ideas that he speaks about, be it colonizing Mars to make humans a multi-planetary species or the hyperloop concept (though there are non-Musk companies that are working on it). The newest in that list of ideas from Musk, one he seems to be quite serious about turning into reality, is tunnels.

Not that tunnels themselves are a new idea, or that they are new to Musk. He had first mentioned it almost a year ago, in January 2016, speaking about how underground tunnels, many layers on top of (or below) each other, would solve traffic congestion problems in high-density cities.

It seemed all but forgotten, just another utterance from a man known to say many things, some of them outlandish. Until early morning Dec. 17, 2016, that is, when Musk took to Twitter to complain about traffic and announced he would build a tunnel boring machine to dig, well, tunnels. There was also a touch of humor.

That he was serious was indicated not just by the last tweet but also at least partially by the fact that he also updated his Twitter status at the time to include the words “Tunnels (yes, tunnels).” The “(yes, tunnels)” has since been dropped as well.

And that he was actually serious became clear in the early hours Wednesday, when he again took to Twitter to reaffirm his earnestness.

And just to leave no doubt of his boring intentions, he confirmed it in reply to a question.

In reply to another question on the social media platform, he also gave the location of the first planned tunnel.

Reducing traffic is an argument that is hard to object to. And with Musk on the Strategic and Policy team of President Donald Trump, who knows where the boring trend might end.