Driving rules in the UK have changed, since at least a decade ago, so that there is no 10% margin. Speedometers are required by law to read on or under and they are more reliable now. So if you're going 36mph then you'd be fined.

On top of the speedometer it has the GPS speed to compare as well, I can't see how there is any excuse for being over the limit.

The quoted stats from UK advertising were that at 40mph 80% of pedestrians will die from the crash, at 30mph 20% will die.

Had the car been doing just under the limt e.g. 33mph then there's a much better chance that the woman would have survived.

I cannot find a reference to backup your claim of the 10% + 2mph margin having been axed. In fact I remembered the Chief Constable calling for the end of it recently (implying it was still being used):

http://www.dailymail.co.uk/news/article-5332443/Police-chief... [30 January 2018]

https://www.telegraph.co.uk/news/2018/01/31/motorists-should...

Can you explain why you think this rule changed a decade ago?

Just what my partner was told when they were caught speeding and offered a course in how to avoid speeding instead of getting points on her licence.

That's not how posted speed limits work in Tempe though. Traffic flows an average of 5-10mph above the posted limit.

Isn't that still too fast? Maybe not worth ticketing for, but still relevant after an incident like this?

So when the road sign says 35mph it means the official speed limit is exactly 38.5mph?

Because sometimes that 10% is argued as a margin of error for humans supposedly not paying attention how fast they're going, but if that's the case then there's really no reason why the robot shouldn't drive strictly under the speed limit.

If you explicitly programmed a fleet of robots to deliberately break the law, then I think it's not enough consequences if you just fine for the first robot that gets caught breaking that law, while the programmers adjust the code of the fleet to not get caught again.

Consequences should be more severe if there's a whole fleet of robots programmed to break the law, even if the law catches the first robot right away and the rest of the fleet is paused immediately.

Should be noted that speedometers display a higher number than actual speed. So if cop flags driver at 38.5 mph, there's a good chance their speedometer showed 40+ mph.