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Fascinating post! I had no idea about this transition from cut-and-cover to TBMs. It's always interesting to see how approaches change as technology advances and the ratio of cost to benefit changes.

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The author paints with too broad a brush. There is significant differences in markets that drive these decisions. Cut-and-cover is standard in my state, but the land cost, density, and regulatory environment allow this. Directional drilling and jack-and-bore is very common for small diameter excavation, though.

> the land cost, density, and regulatory environment

Cheap land, low density, lax environmental regulation?

Correct. A major cut and cover in downtown Dallas would be insane. Bringing a TBM to put in a tunnel for bikes in Springdale Arkansas would be insane.

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