WSJ looks into this particular crash NHTSA is investigating. It shows how the Autopilot system was able to see some cars earlier in the drive, but then how it failed to notice the police car with flashing lights in its lane. Ultimately resulting in a 55mph collision.
What I’m getting from this is take control of your vehicle immediately when you see flashing lights.
Teslas are known to have an issue against 0mph objects, be they cars with flashing lights, trucks (https://www.theguardian.com/technology/2016/jun/30/tesla-autopilot-death-self-driving-car-elon-musk), or child-mannequins (https://www.youtube.com/watch?v=tDrbUO7KR-0)
If there’s ANYTHING sitting still on the road, assume that the Tesla system CANNOT SEE IT.
Honestly, with the latest update, it’s struggling with stop signs.