EDIT: refers more to cost, and not directly time. Musk claimed[1] existing tunnels are far too big/wide as they're over-engineered for safety + regulatory FUD.

EDIT: refers more to cost, and not directly time. Musk claimed[1] existing tunnels are far too big/wide as they're over-engineered for safety + regulatory FUD. Boring plans to reduce tunnel diameter by half (from 28ft to 14), and then build a better machine to tunnel + support the walls simultaneously. Estimates would reduce costs by ~10x. [1]: https://youtu.be/zIwLWfaAg-8?t=3m10s https://youtu.be/zIwLWfaAg-8?t=3m10s