The Boring Company Loop system pic.twitter.com/xVpDHzZKXB

— The Boring Company (@boringcompany) December 19, 2018

Elon Musk may have just disrupted another industry. In this case, it’s transportation tunneling. His Boring Company last night unveiled a 1.14-mile “proof-of-concept tunnel” in Hawthorne at a cost of $10 million (see Twitter video above).

As Alissa Walker described in Curbed LA after attending the launch, the tunnel features a track for a Tesla to drive underground, as a sort of subway transit for private vehicles. While the tunnel is getting a lot of press, transit advocates have concerns about how effective this type of private transport might be.

But perhaps more important is Musk’s potentially significant advancement in tunneling technology, which could offer major benefits for subway tunneling everywhere (and maybe even please those same pro-transit critics).

Bloomberg summarized the engineering progress:

Musk said that the advances his team has made in tunneling technology would increase the speed of boring underground by up to 15 times. The company will do that largely through tripling the power of the drill itself, he said, and through logistical interventions such as building segmented reinforcements in the tunnel walls while continuing to drill.

Given the numbers that Musk reported last night, he may have netted significant results, with a relatively minuscule price of $10 million for 1.14 miles.

By comparison, recent per mile tunneling costs around the country have been staggeringly high, as Alon Levy noted in CityLab. For example, New York City’s recent Second Avenue Subway clocked in at an astounding $2.6 billion per mile. San Francisco’s central subway and Los Angeles’s regional connector subways are not much better, at $920 million per mile, while the L.A. Purple Line subway may cost $800 million per mile. That means these major transit system tunnels are costing as much as 100 times more than Musk’s prototype tunnel.

But are we comparing apples to apples? Not really. The costs described above include much larger diameter tunnels, as well as station “boxes,” utility relocation, ventilation, and safety features, among others. As Alon Levy calculated back in 2017, even in a best-case scenario with cheaper “cut and cover” station boxes, U.S. subway tunneling would likely still cost $500-600 million per km ($800-$960 per mile). Musk’s tunnel by contrast is quite bare bones, with no station boxes or complex systems and space for only one vehicle.

For a better comparison, we can look to Laura Nelson’s reported numbers for the Purple Line heavy rail extension in the Los Angeles Times. She described back in June the tunneling contract for the 2.59-mile extension from Century City to West Los Angeles, which is projected to cost $3.59 billion total. But the actual tunneling contract is smaller: $410-million for a four-year design and construction contract to Tutor Perini. So the costs just for tunneling (assuming these numbers will be accurate, which is doubtful based on past experience) will be $158 million per mile, not including land acquisition and moving utility lines.

But that $158 million per mile is still 15 times the cost of Musk’s Boring Company tunnel.

Ultimately, more analysis and investigation will be needed to understand how the costs for Musk’s single-track tunnel might compare to a large-scale, twin-bore subway tunnel with all the safety, lighting, and ventilation features that we see in big urban transit projects.

But the early numbers indicate that Musk may have just achieved a significant breakthrough in reduced tunneling costs, with major benefits for transit everywhere.