The default speed limit will be lowered to 20mph on the majority of roads in urban and built-up areas across Wales from Sunday.
Described as the ‘biggest step-change in community safety in a generation’, most streets in Wales that currently have a 30mph speed limit will switch to 20mph, as the country becomes the first nation in the UK to reset the default speed.
Once the change comes into force, more than 12,000km of roads will have a 20mph limit.
Wales' First Minister said the change was being brought in to make streets quieter, reduce noise pollution, and the number of serious casualties that happen on roads.
The new limit be enforced by the police, local authorities and GoSafe, which is an engagement and enforcement body that works with the Welsh government and the police.
Speaking in the Senedd on Tuesday, the Deputy Minister for Climate Change, Lee Waters vowed that they would not "come down like a tonne of bricks on people doing between 20 mph and 30 mph as it beds in".
So if you are caught driving over 20mph, will you get a fine?
The answer: Maybe. Maybe not.
As people get used to the new rules, the authorities enforcing the limit are keen to take an educational approach.
Officers have power to pull over drivers who are exceeding 20mph on a restricted road.
They say their response will be proportionate to the speed the driver is going.
If you are pulled over by an officer, they can fine you. However, whilst drivers are getting used to the rules change, the police could give you advice on the new limit as part of the education push.
They might also, ask you to watch a presentation about the speed limit. This will be given by a member of the fire service or GoSafe staff.
There are various locations across Wales, which are identified as high risk, where GoSafe and the fire service will give these presentations.
However if drivers are deemed to be driving at a dangerous speed, more robust action will be taken.
Community Speedwatch (CSW) is also playing a role in the enforcement. If you are caught exceeding by CSW, you might have your details passed onto GoSafe, who will issue you with a letter.
Fixed cameras will be adjusted down to 20mph on Sunday. This means that if you are caught driving over the limit by a camera, you could be fined.
In June, more than 30 new speed cameras were installed across Wales. Some roads now have multiple new cameras.
Any money that is made through 20mph fines as the rollout continues won't end up in the Welsh Government's pockets. All the money will go to the UK Treasury.
First Minister Mark Drakeford has welcomed the change. He said “I’m very pleased indeed that we are introducing this,” adding: “There will be a measurable reduction in the number of children killed in Wales as a result of this policy and it returns the streets to the people who live [there].”
The policy has proven controversial, with more than 70,000 people signing a petition to scrap the speed reduction. Only on Thursday, Leader of the House of Commons, Penny Mordaunt said the change is “absolutely insane”.
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