Jane Dodds believes cutting some urban road speed limits from 30mph to 20mph from September will save lives.
The Mid and West Wales MS said at the Senedd that it’s important to look at the evidence produced by experts on road safety.
She said it shows that lives are saved at slower speeds, with people involved in collisions at 20mph having better survival rates than those involved in collisions at 30mph.
Ms Dodds said: “Public Health Wales say the lowering of the speed limit will save an estimated six to 10 lives and between 1,200 and 2,000 casualties every year - saving the health service between £58 million and £94 million. That is going to mean more nurses and more doctors.”
She suggested that the Welsh Government needs to be clearer about why the change is being made.
Ms Dodds believes it will help create a safer, healthier and a more liveable Wales with fewer road accident deaths and injuries.