My heart breaks for the driver's family and friends. I hesitate to even discuss the technical details of this accident because the most important thing here is that a person lost their life, and it shouldn't have happened. But I think discussion is valuable in the context of saving lives in the future.
I'm eager to see the NTSB report when it's finished. But from what I've read so far, I think responsibility can be divided between three parties, in the following order:
1. The driver
I assign the most responsibility to the driver only because the driver of a vehicle always has a responsibility to be in control of that vehicle. It's not victim-blaming to say that the person operating a car might have been partially responsible for a car crash.
That said, I strongly feel that Caltrans bears significant responsibility for this accident. The only reason I assign more responsibility to the driver is that the driver is ultimately the one most able to adapt to less-than-ideal circumstances in the moment. But as far as I'm concerned, this crash was preventable and Caltrans is the entity most at fault for failing to prevent it.
Collisions with this same barrier at this same interchange are so common that Caltrans can't even manage to keep the crash attenuator — which is meant to absorb an impact rather than allowing a car to run directly into the concrete barrier — in good repair. After an impact, the crash attenuator must be replaced, but Caltrans has frequently failed to replace the attenuator at this location. When the Tesla hit it, it was already collapsed and provided no protection.
Furthermore, the entire interchange is poorly designed. The white lines on the approach to the barrier appear to form a lane. There are no painted hash marks indicating that the area is not a traffic lane or hinting that there's a barrier ahead. From a distance, the barrier is difficult to see even on a clear day due to its short height and narrow width.
Human drivers are confused by this interchange often enough that it's a frequent location of accidents. Why hasn't Caltrans improved it? Why haven't they at least painted hash marks across the approach to more clearly indicate that it's not a lane? Why haven't they mounted a larger, more visible warning sign and a flashing light on the barrier to make it more visible? This is inexcusable negligence.
I assign the least amount of responsibility in this incident to Tesla. Tesla is very consistent about describing Autopilot as a driver assistance system. When the driver engages Autopilot, a warning is displayed informing them that they must still monitor and maintain control of the vehicle, and that they must keep their hands on the wheel at all times.
Tesla is transparent about Autopilot's limitations in their manuals and marketing material. Autopilot is not good at detecting small stationary obstructions in the road. It's not good at discerning between actual lanes of traffic and markings that just look like lanes. It's not good at handling unusual scenarios. This is why it requires constant human attention, with hands on the wheel and eyes on the road.
Autopilot can improve, and I expect it to, but I don't blame it for this accident. I think driver assistance technologies like Autopilot are far more beneficial to safety than almost any other advancement in automobile technology, even though they're still far from perfect.