I believe it’s one out of every three miles must straight as a pin. Sometimes they double them up.
“...it’s one out of every three miles must straight...”
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Depends on terrain. Ike was educated by the Bocage in France:
https://en.wikipedia.org/wiki/Bocage
He designed the Interstate Highway to not repeat that. As a plus, the unemployed GI’s from WWII and Korea had a job available.