Elon Musk said on Twitter that he received “verbal government approval” to build an underground Hyperloop transit network connecting New York, Philadelphia, Baltimore and Washington DC, with stops connecting each city center, and a dozen more entry or exit elevators located within each city. The project would be run through The Boring Company, Musk’s tunneling venture, which has already begun test digging near SpaceX HQ in California.

Just received verbal govt approval for The Boring Company to build an underground NY-Phil-Balt-DC Hyperloop. NY-DC in 29 mins. — Elon Musk (@elonmusk) July 20, 2017

Musk didn’t share any additional details about what he means by “verbal” approval specifically, and we’ve reached out to The Boring Company to find out more details. When the SpaceX and Tesla founder revealed the details of his future vision for The Boring Company, however, he described a network of underground tunnels that would transport goods on sleds, and that could offer transportation for cars, cargo and more, using Hyperloop as one potential conveyance option.

City center to city center in each case, with up to a dozen or more entry/exit elevators in each city — Elon Musk (@elonmusk) July 20, 2017

In the original tweet, Musk noted that the trip time from New York to DC would be just under half-an-hour. Currently, by train, that trip is roughly three hours and 20 minutes, or over four hours by bus. Musk also said that an LA to San Francisco loop is likely on the horizon, as well as a loop to connect Texas to the network.

Musk also originally came up with the concept for Hyperloop, though he opened up the idea to development by outside interests because he said at the time that he would not have enough time to devote to making it a business in its own right, in addition to his other duties. It’s not clear whether the Hyperloop component of this project would be developed by The Boring Co. itself, or by an outside partner focused on the tech, like Hyperloop One, for instance.

It’s also unclear what exactly Musk means by “verbal government approval,” [Update 11:41 AM PT: Bloomberg reports it was approval from within the White House] and whether that means he has the ‘okay’ to proceed with a proposal, or to actually start digging. Plus, it’ll likely require many more formal written approvals before anything can proceed.

Hyperloop One CEO Rob Lloyd has discussed how use of its tech could transform communities, and have a similar physical transportation globalizing effect to the impact made by broadband on digital communications. Connecting these communities via transit that cuts commute and cargo times to below what you would expect for getting place-to-place within any one of these communities would undoubtedly have a tremendous economic and social impact.

During an interview at the International Space Station R&D conference on Wednesday, Musk talked briefly about The Boring Company, noting that “oddly enough it’s kind of like a little low stress activity, because everyone expects us to fail.”

Musk later tweeted that there is “still a lot of work needed to receive formal approval,” which is likely an understatement to say the least with a project of this scope.