Considering it costs $1 billion per mile to dig L.A.'s subway tunnels, how does Elon Musk plan to build a series of car-carrying tunnels with out breaking the bank?

Elon Musk is serious enough about his plan to build tunnels for cars below L.A. that he has at least given thought to the huge hurdles his plan will have to overcome—namely, the cost of engineering such an endeavor. Ruth Reader of Fast Company writes that the entrepreneur plans to dig the tunnels in a much more cost effective manner, "correcting inefficiencies" in the process.
(Musk) plans to make the diameter of the tunnels only 12 feet wide, much smaller than the typical 26-28 feet. He also says that a machine that tunnels and reinforces continuously will allow the burrowing process to go more quickly—especially if he were to increase the power of such a machine.
Elon Musk's discussion of the tunnel project and the Hyperloop transportation system from the TED2017 conference can be viewed online here.
FULL STORY: Elon Musk Shows Off A “Boring” Tunnel Network To End L.A.’s Traffic Jams

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Planetizen Federal Action Tracker
A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

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Report: Zoning Reforms Should Complement Nashville’s Ambitious Transit Plan
Without reform, restrictive zoning codes will limit the impact of the city’s planned transit expansion and could exclude some of the residents who depend on transit the most.

Judge Orders Release of Frozen IRA, IIJA Funding
The decision is a victory for environmental groups who charged that freezing funds for critical infrastructure and disaster response programs caused “real and irreparable harm” to communities.
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