It is impossible to determine the positive impact of 20 mph speed limits on these statistics. This is no different to not being able to see how ADAS, air bag technology, redesign of bumper mechanisms and crumple zones, enhanced pedestrian areas, traffic calming measures in accident hot spots, road safety awareness initiatives, the rise in black box insurance policies, and so on influence the stats. The downward trend of the last ten years is the sum of all of these. Concerning the 20mph topic, political point scoring is inevitable.