In 1925, several American highway associations drafted up designs for a six-lane highway running from NYC to Washington DC. This doesn't sound controversial, but they also decided to plop down the road adjacent to the White House and Capitol.
This proposed motorway (dubbed the "Lee Highway") was part of a greater plan to unite the nation with a massive Autobahn-like road system from sea to shining sea. The thing is, the designers thought it was a fine idea to to toss the highway smack dab through Washington DC along Pennsylvania Avenue. Automobiles and national security concerns of the 1920s weren't what they are now, but it's nonetheless a bizarre notion to put a roaring road within earshot of the Rose Garden. You can read more about this never-was, snafu-prone plan over at Ptak Science Books.