Little evidence 20mph speed limit reduces casualties, says report

This Guardian report https://www.theguardian.com/world/2018/nov/23/little-evidence-20mph-speed-limit-cuts-casualties-says-uk-report says it all when you look at the first and last sentence:

'There is insufficient evidence that a 20mph speed limit has led to a significant reduction in the number of crashes and casualties in UK residential areas, a government-commissioned study has found.

... 

Joshua Harris, the director of campaigns at the road safety charity Brake, said: "Breaking the speed limit is breaking the law and those who do so should be punished. We must make a success of 20mph limits, but to do so we need more enforcement, which is delivered consistently across the country."'

In other works, it doesn't matter if the 20mph limits make a difference so long as drivers are punished.