Earlier quoted context omitted.
I think the answer is that the path into the barrier looks just like an actual lane, and that this was enough confusion that a human driver apparently had made the same exact mistake a week earlier. https://imgur.com/a/iMY1x https://techcrunch.com/wp-content/uploads/2018/03/screen-sho...
Except those solid white lines delimit an uncrossable barrier delimiting the HOV-specific (during commute hours) flyover from the 101 lane, which is well documented for nearly a mile preceding that point.
There's a spot just like this in Houston on 610 East. HUUUUUUGE flyover as the HOV lane spends about a half mile merging into the left lane of 610 (nice fat fast freeway, they need the runway). A guy had thought the flyway would be a safe place to park his car and wait for a tow. Safe enough that he was sitting on the hood of his car. Sure as shit the Challenger in front of me got confused, cut into the flyaway thinking it was a lane, hit the disabled car, and sent the guy flipping up into the air a good 10, 15 fit. Fucked up accident.
Anyway point is after the accident I was talking to the driver of the Challenger, trying to calm him down (kept saying "holy shit I fucking killed that guy!") and other that shock he was sober as a duck. He got bloodtested and everything, clean. In court he said he just got confused and thought it was a lane.
LONG STORY SHORT human error mang, human error. Still not sure why a car was able to do it.
They have those same white lines leading into intersections and people cross that shit all the time. People speed.