I see 2 very likely scenarios.
1. He could have been murdered somewhere else and then the person who killed him drove his car to where it was found, placed his body where it couldn't be found easily and then put the car in gear and made it look like he had an accident?
2. He was using drugs, had been at a party or something, headed home, got lost (because he was under the influence), he was overdosing and slowly drove his car off the highway, hit a tree, got out and wandered off in a drugged stupor and died from an overdose.
I am leaning towards #2, but think it could be either way.
I cannot figure out what he was doing in that part of the state. He was a pretty long way from home, the only place that road goes is to San Angelo and on to Mexico. Not a likely road trip in my opinion.
No disrespect meant to Joseph here either. Just speculating to COD.