The Welsh Government will be the first in the world to reduce limits on residential roads from 30mph to 20mph in a bid to encourage people to walk and cycle more.
But a petition opposing the plans has already gained more than 38,000 signatures and opposition politicians have slammed the “ridiculous” £32m plans.
Buckley resident Adie Drury started the petition after her hometown was used as a pilot area for the scheme.
He said: “It is causing chaos, people are avoiding the area and people are having to use new routes.
“Many of these roads are not suitable for a 20mph speed limit. They are busy access roads on steep hills.
“Trucks struggle to climb hills in such a low gear and maintain such a low speed downhill on the brakes.
“This does nothing to reduce emissions, but there will be more pollution from more cars struggling in a lower gear for longer.
Proponents of the rule change say the chances of someone surviving a 20 mph collision is seven times greater than at 30 mph.
Mark Drakeford, First Minister for Wales, said: “We know that 20mph zones reduce traffic speeds, reduce accidents, especially accidents for children. We want this to become the default position across Wales them”.
The Welsh Government says the move will save £58m over 30 years due to reduced demand for emergency services and hospital treatment.