The Boring Company's second Nashville tunneling machine is ready to dig
The Boring Company has declared its second Prufrock tunneling machine, MB2, ready to mine under Nashville as part of the Music City Loop project. The machine passed its commissioning cycle — including an 11 rpm rotation test — and will now join MB1, which has already been digging. With a third machine, MB3, confirmed to ship in August 2026, the company is building a case that it can manufacture tunnel-boring equipment at speed.
The machine
MB2 is a direct iteration on MB1, not a redesign. It runs with 15% more power and uses 17-inch disc cutters, up from MB1's 15.5-inch, giving it more bite through rock. Like its predecessor, MB2 is fully electric and operates with zero workers underground during normal tunneling — a control room on the surface handles everything. The Prufrock operating model also allows the machine to "porpoise" — angling down from the surface without a purpose-built launch pit — and resurface at the other end, cutting weeks off typical setup time.
The traditional tunnel-boring approach stops constantly: drill a short section, halt, install concrete wall segments, move forward. Prufrock is engineered to line the tunnel while it digs, eliminating those stoppages. That parallel workflow is central to The Boring Company's speed argument.
Prufrock-MB2 is ready to mine in Nashville! MB2 commissioning is complete, including the brief 11 rpm rotation shown here.
— The Boring Company (@boringcompany) June 17, 2026
Will MB2 catch up to MB1, who had quite the head start?
And Prufrock-MB3 ships in August! pic.twitter.com/TTrMql2aRg
Nashville as the proof point
The Music City Loop is a planned 13-mile twin tunnel connecting Nashville's airport to downtown. The Boring Company estimates the project will cost $240–300 million total, or roughly $25 million per mile, per Tennessee Lookout cost analysis. Traditional urban light rail routinely runs $200 million or more per mile, so if those numbers hold, the comparison is striking. The project has secured 37 of 45 required permits; a TDOT tunnel permit already authorizes up to 25 miles of tunnel, and federal approval from FHWA came through in February 2025.
The only live reference point for Boring's model remains the Las Vegas Loop — a smaller, lower-traffic system that carries passengers in Tesla vehicles through a single-lane tunnel beneath the Vegas Convention Center. Nashville would be a substantially larger test.
MB3's August 2026 ship date signals that the company sees its manufacturing process as repeatable. Teslarati's MB2 commissioning report notes that lessons from MB1's operation sped up MB2's commissioning considerably. Whether that translates into faster dig times — and whether the $25 million per mile figure survives contact with a full-scale urban project — is still the open question.
