the interstate highway system

 

 I always knew there was a logic to it, but I never saw it explained so well until I stumbled upon this delightfully informative short video on how the US interstates are numbered.

Those with 2-digits traverse the entire country

If they end in "0" they run East-West (10, 20, 30, ..)

If they end in "5" they run North-South (5, 15, 25, ..)

Those with 3-digits are bypasses and contain the last 2 digits of the interstates they bypass.

That's it! (plus exceptions)

https://www.youtube.com/watch?v=8Fn_30AD7Pk

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