An "Easy Rider" type of song. The movie came out in June 1969. Other biker films before this one The Wild Angels (1966) & The Trip (1967). So it does not surprise me that The Doors made an "Easy Rider" type of as song - "Easy Ride". It a great song for fans of easy riding music.
Listening to the 4th album "The Soft Parade" released on July 21, 1969 at this point Mr Morison was succumbing to alcoholism and had lost control of himself and the respect of his band mates. Review from the August 22, 1969 "Rolling Stone Magazine" (the Bible of the period) by Alec Dubro: http://www.rollingstone.com/music/albumreviews/the-soft-parade-19690823