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.