Apparently my stored links on this topic are dead but two worhtwhile pieces of information on that point
1) drivers who consistently drive below the average speed of other drivers on a road (i.e., who religiously drive the speed limit) are more likely to be involved in crashes
2) More accidents are caused by speed differential than by speed by itself.
Your assertion (true or not) is irrelevant to this case. This was a car impacting a pedestrian, not another car on the road. In any impact between a car and a pedestrian the speed of the car is critical in determining whether the pedestrian will be killed.
I didn't mean to suggest that it was relevant in this case. I was merely providing some context for the parent post's observation about an automous car exceeding the speed limit
1) drivers who consistently drive below the average speed of other drivers on a road (i.e., who religiously drive the speed limit) are more likely to be involved in crashes
2) More accidents are caused by speed differential than by speed by itself.