Do you know of an example where speed limits being a non-enforceable recommendation has actually proven anywhere near as effective in reducing road fatalities a

Do you know of an example where speed limits being a non-enforceable recommendation has actually proven anywhere near as effective in reducing road fatalities as legally enforced limits? And how far do you want to push this argument- that if I choose to drive an unroadworthy unregistered vehicle at 200kph on the wrong side of the road while highly intoxicated, I shouldn't be fined unless I provably cause injury/death/property damage to others?