Okay, I've heard that 40mph plenty of times here when AI cars come up, so is it possible the car could have slowed down 10mph? I only suggested 10km/hr as an ideal maximum (aka 35mph) given better technology, not as a baseline for today...

I've also read that the last speed sign was 45mph before this accident. I used 40mph as it was between the 35mph sign that was coming up before the hit and the 45mph one before it.