From next week the default speed limit for most 30mph roads will be reduced to 20mph.
The Welsh Government say that reduction will make the country a safer and greener place to live but opponents argue that the costs of the scheme greatly outweigh the benefits.
But love it or loathe it, the rules are changing so, here's everything you need to know.
When does 20mph in Wales start?
From midnight Sunday 17th September, 2023.
Wales will become the first UK nation to introduce the default 20mph limit.
How do I know if I'm driving on a 20mph road?
The 20mph limit will be in place on what are called 'restricted' roads. These are roads in built-up areas, where there is high pedestrian activity.
According to the Highway Code, you can identify these types of roads because they will have streetlights spaced no more than 200 yards apart.
That means there won't necessarily be a 20mph road sign - you should assume a road that used to be 30mph is now 20mph.
Will there be any 30mph roads left?
Most residential roads across Wales which are currently 30mph will be slowed down to 20mph.
However, there are some exemptions to the new rules and local authorities have been able to keep some roads at 30mph. There's no cut-off date to exempt a road - councils can continue to do this after Sunday 17 September.
There will be 30mph signs in place to tell you if this is the case.
You can see a Welsh Government map of exemptions here.
How will it be enforced?
You can be caught speeding by a speed camera or a police officer.
In June, more than 30 new speed cameras were installed across Wales. Some roads will have multiple new cameras.
Immediately after the implementation of the limit, some drivers might not receive a fine.
Instead in some instances, fire service staff and GoSafe staff will enforce the limit. They will show speeding drivers an educational video on the dangers of driving above 20mph.
This is what has happened in some of the trial areas over the last year.
How much could I be fined?
At the moment the minimum penalty for speeding is £100 and three points on your license.
If you accumulate 12 points on your licence you will be disqualified from driving for at least six months.
If a speed camera catches you exceeding the limit, you will be sent a fixed penalty notice (FPN).
If police stop you, they can give you a verbal warning, issue you with an FPN or order you to go to court.
You may be given the option to attend a speed awareness course depending on the speed you were caught travelling or if you have not been on one in the past three years.
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.
Who decided this?
This rollout next weekend is years in the making.
In early 2021, the Welsh Government announced they would be trialling a default limit in 8 locations across Wales, including Abergavenny, Buckley and Llanelli North.
During the trials, the Welsh Government released polling which suggested that four in five Welsh adults (80%) said they would support a speed limit of 20 mph in the area where they live, compared to one in five (20%) who would not.
However, tens of thousands have signed online petitions opposing the plans.
In July 2022, Ministers voted to change the law to make 20mph the norm. They say research shows that changes will reduce pollution and fatal crashes.
Does it work?
There has been a great deal of political 'toing and froing' over the efficacy of the scheme.
Since announcing the plans the Welsh Government has been on a campaign to promote the evidence from other 20mph implementations in the UK which showed small reductions in average speeds where people live and work can result in reduced collisions and serious injury.
However, another report was released that suggests that cutting speed limits on urban roads to 20mph does not significantly improve safety.
The report, published in the Journal of Epidemiology and Community Health, analysed data from before and after the limit was introduced on 76 roads in central Belfast in 2016.
Comparisons with streets in the surrounding area and elsewhere in Northern Ireland that retained their 30mph or 40mph limit showed there were “no statistically significant differences” in terms of the number of crashes, casualty rates or average traffic speed.
Speaking to ITV Wales, the mayor of Bristol praised Wales for its "courage" in introducing the new laws.
The English council introduced the limit there in September 2015.
The mayor said: "The logic is 20mph eases the flow and it doesn’t slow you down and your journey across the city."
Speaking to ITV News, taxi drivers who have been working in the pilot locations say the scheme costs them more money in fuel every day.
Alex Leonard, a Cardiff cabbie, said: "Every day I filled up my tank and it would be an average of £7 more a day."
He said the policy means "slower jobs", explaining that the customer will then have to allow more time to get to their train station.
What do the politicians say?
The speed limit change has become a political battleground since the policy was first proposed in 2021.
The Labour-run Welsh Government has argued that the scheme is aimed at reducing the number of fatalities on roads and making the country greener.
Lee Waters MS, the Deputy Minister for Climate Change, has been the driving force behind the policy.
He has described it has "the biggest step-change in community safety we have seen in Wales for a generation."
Adding: "In Wales, we do things differently, we look after each other and trust the science.
"Evidence shows that a vehicle travelling at 30mph will still be travelling at 24mph in the time it would take a car travelling 20mph to stop."
The Welsh Conservatives have been highly critical of the policy since the pilots started.
Their leader in the Senedd, Andrew RT Davies, told ITV Wales: "Having 20mph as a default is the wrong option for the Welsh Labour Party government. It's going to cost the Welsh economy £4.5 billion - that's their own figures.
"That's not what the people of Wales want to see."
How much is it going to cost?
According to numbers from the Welsh Government, the roll-out of 20mph on residential roads in Wales is expected to cost an estimated £32.5 million. Most of that money will go towards changing road signs and repainting roads.
The Welsh Government say they will need 30,000 replacement signs and 5,000 posts.
Another £1.6 million will go towards national and local communications campaigns. That ranges from TV and radio adverts to leaflets through your door.
First Minister, Mark Drakeford, says the costs are worth it in the long term. He said "It will save £92 million every year for the NHS alone. So sometimes you have got to spend to save."
He's making reference to a report by Edinburgh Napier University which estimated the casualty savings of 20mph to the NHS.
The Welsh Conservatives have taken aim at the costs of the scheme, saying that the real costs to the Welsh economy will be more than £4 billion.
Welsh Conservative Shadow Transport Minister, Natasha Asghar MS said: “This pet project by Labour is going to cost the Welsh economy £4.5 billion, slow down emergency services and will ultimately cost more lives than it saves."
The £4.5 billion figure is the Welsh Government's own prediction.
In fact in their analysis of "dis-benefits", they predict that, without considering the potential savings, the scheme could cost £6.4bn to the economy over the next 30 years.