originally 1 mile in every 5 was to be straight, so that is could potentially be used as a runway.Urban legend.
I stand corrected. My main point was that Eisenhower wanted a national road system to help for the defense of the country. In his early career, he was tasked to travel over the country to look at the conditions of America’s roads. When he was in Germany, he was impressed with the autobahn and how it support German, and ironically, allied troops with supplies.