That's interesting. Because Cassady and Kerouac's road trips in "On the Road" happened in 1947, 1949, and 1950 [0]. Construction of the Interstate Highway System didn't begin until 1956, and didn't finish until 1992 [1].
However, if we conspicuously omit the name "Kerouac" and that most famous of American counterculture roadtrips, then like Fred Turner, we too can conclude that no fun ("heroic!") roadtrips happened prior to intervention by the Federal Government.
[0] http://www.dennismansker.com/ontheroad.htm
[1] http://en.wikipedia.org/wiki/Interstate_Highway_System#Const...