That's precisely my point: with that approach they'd have to dig an parallel 230 mile tunnel just for emergency access. Plus cross passage escape tubes that you

That's precisely my point: with that approach they'd have to dig an parallel 230 mile tunnel just for emergency access. Plus cross passage escape tubes that you can get to on foot before you're overtaken by smoke or gases. The Gotthard tunnel has them about every half mile, but the Boring Company will use smaller diameter tunnels where smoke and gas spread faster, so they'll probably need them more tightly spaced -- say, every quarter mile. And they'll use separate tunnels for each direction of traffic. So that's three tunnels plus 230 x 4 x 2 = 1,840 cross passage tubes. This is all technically achievable, but the Boring Company's vision is all about cost.. building tunnels 10X cheaper. This is, I think, at least as great of a challenge as getting government approvals to dig very deep.