Petition against 20mph blanket speed limit

[Eric the Half a Bee]

isn't this more about air pollution than accident rates?

The primary reason the Welsh Government keep saying is a reduction in fatalities and serious injuries, reducing the pressures on the NHS. I understand that 20mph in 3rd gear produces the same emissions as 30mph in 4th as revs are virtually the same.

In the link I provided earlier, Professor Cole says one reason for the speed reduction is to make car travel less attractive. In other words, the Welsh Government know that we can't keep putting more and more cars on the roads and this will hopefully result in fewer car journeys.