On: Tunnel Boring Machines (2018)

[spullara]

Or you could just move the surface streets a couple of stories up like they did in the early 20th century in Chicago. Trucks (for deliveries, etc) are not allowed on the surface, only below.

[djsumdog → spullara]

A lot of early cities jacked up their buildings. Chattanooga did due to flooding.

I somehow doubt such things could happen today considering the superstructure foundations under a lot of our modern buildings.

[cududa → djsumdog]

The only time cities have jacked themselves up is after fire or natural disaster. No way “underground deliveries” is scalable.

[spullara → djsumdog]

Definitely easier to keep the buildings at their current level and just make a new entrance on the second (or higher) floor.

[lmm → spullara]

You can't bootstrap having a nice walking environment at above-ground level that way. Who's going to open the first cafe where there's no foot traffic? Why will anyone spend a lot of money on entrances that no-one's going to walk to? What pedestrian is going to want to keep walking up and down stairs while the network is partially complete. The City of London tried to do what you're suggesting and it was a total failure, because while it might have worked if it could have magically all been done in one go, there's no way to get to there from here.