What are you talking about - the Wales experiment as you called it has clearly shown it's a good idea - I wish it was implemented everywhere now and the numbers clearly support it. It's only being raised back up to 30 in areas where

1) the data suggests no improvement(which was always the intention of the change)

2) the issue became political and the limits are raised no matter what the data says

Overall for Wales the improvement in safety has been undeniable though and it's hard to disagree with it.