In an interview with David Letterman, he said he had wanted to do this after seeing Captain Dynamite. He asked Rice for permission to use the stadium, but they turned him down. I didn't know he had actually gone through with it.
RE: Dennis Hopper, the Media Center, and the Death Chair
Hopper actually came to Brian Huberman's 'Western Film Genre' class and talked to the class the day immediately preceding the Texas Race Course stunt, Huberman screened 'Easy Rider' for that class, and Hopper had a long 'director's cut' session for the class. Immediately after he took a Q&A session from the class. During that session he announced what he was going to do and invited the class out to witness everything. Apparently everything about 'Easy Rider' was off-the-cuff with only a rough outline put forward by Peter Fonda on what would happen. Pretty much most of the movie was based off ideas for a filming day based on the drug and booze get togethers from the night before.
I wasnt in the class, but had some very good friends who not only were in the class session and also motorvated to the Raceway to see the stunt.
I took the class the next year, and Huberman throughout the semester kept talking about that class session and how he was the person who filmed the next day's stunt.