Let me throw out my current theory: Bryce was intending to go home to discuss whatever the thing was that he said he had a lot to talk about. But I don't think he wanted his parents to know. He just wanted to "show up". He wanted to talk face to face & didn't want to alert them to his coming because he felt they would tell him he couldn't - too long a drive alone, not safe, etc, and/or start pumping him for information about what he wanted to discuss, which he didn't want to get into until he was there & could lay it all out.
He knew very few people in Southern California at all. Those he did have to have been checked out and/or would have come forward by now if went there or was expected to show up but didn't.
Delays in Buttonwillow: I think was a combination of sleeping & crashing down from being wired / high. He ran out of gas at a rest stop. That doesn't happen unless you are parked there with your car running for an extended period. The drive into the rest stop area is much to far to "coast" after running out of gas. He was sleeping with the AC on & ran out. He later went further down the freeway to the truck stop area, likely for food. I guessing he had some cash.
He was hanging out there for the same reasons mentioned above & just overall "out of it" from extended sleep deprivation. He was trying to clear his head & figure out what he was doing. Maybe rethinking his original plans after being a little more clear headed. Once he was on the phone with his mom, it appears he was attempting to head home. The route through the grapevine was riddled with massive construction & detours (thanks Ghost for the reminder!).
He finally got to Castaic & wanted to pull off. Some people just CAN'T stay awake driving in the middle of the night to save their lives. My husband is one of them, even at Bryce's age. Either that, or he just wasn't ready to face mom - maybe she was angry on the phone with him a few hours before or during the 1:50am call. She expressed frustration in MSM interviews of his comments of not knowing where he was on I-5 & detouring off the freeway. If she expressed frustration in an interview, I find it very possible she expressed it much stronger to Bryce on the phone. I know I would have been upset with my child at that point, not knowing what all we know now.
What happened after the accident, I have no idea. But I don't believe it was intentional.
What he wanted to talk about, I've always thought he wanted to go home to Illinois. Uprooting an 18 yr old, just out of high school, to half way across the country would be VERY hard on the teen psychologically.
:twocents: All this JMO.