The American economy is underpinned by networks. Road networks carry traffic and freight; the internet and telecommunications networks carry our voices and digital information; the electricity grid is a network carrying energy; financial networks transfer money from bank accounts to merchants. They’re vast, often global systems—but a local disruption can really block them up.

For example, the I-85 bridge collapse in Atlanta will affect that city’s traffic for months. A seemingly minor train derailment at New York’s Penn Station resulted in multiple days of travel chaos in April 2017.

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