No idea if there has been a road movie marathon, but some to consider:
Apocalypse Now (1979) - One of the greatest road movies, even if the road is made of water
Highway 61 (1991) - A lessor known movie, with a nice cameo by Jello Biafra for fans of the Dead Kennedys
O'Brother Where Out Thou (2000) - For the Coen Brother fans
Duel (1971) - To bring out a sweat
Fear and Loathing in Las Vegas (1998) - To bring on a flashback
The Hitcher (1986) - To make your skin crawl
Musa: The Warrior (2001) - A sandy road on horse back
Pee Wee's Big Adventure (1985) - A bicycle road movie
There are lots more, but these are a start.