Drivers are being warned not to rely on sat navs for the speed limit on Welsh roads when they change from 30mph to 20mph this weekend.

Wales will become one of the first countries in the world, and the first nation in the UK, to lower the default national speed limit on residential roads to 20mph on Sunday (September 17).

First Minister Mark Drakeford said the speed limit reduction will protect lives and save the NHS in Wales £92 million a year.

Drivers warned not to rely on sat nav after 20mph speed limit change

The RAC said motorists should “pay full attention” to signs rather than their sat navs after the 20mph change is made on Sunday.

RAC head of policy Simon Williams said: “It’s vitally important that drivers are fully aware of the arrival of the 20mph limit in Wales, and pay full attention to all road signage.

“And, until sat nav systems have been fully updated, they shouldn’t rely on them to know what the speed limit is on any particular stretch of Welsh road.”

Mr Williams said he agreed with the new speed limit, adding: "Even if compliance with new 20mph limits is poor, it should lead to an overall reduction in speeds which will have a positive effect on road safety.”

Wales 20mph map - all the roads affected by the speed limit change and those that are exempt

From September 17, 2023, all residential roads in Wales will be reduced from a 30mph to 20mph speed limit. 

However, there will be some exemptions. 

You can see all the roads set to be impacted by the speed limit change, and the ones that will be exempt on the DataMapWales map.

The Welsh Conservatives, who are opposed to the rollout, said there are Welsh Government documents that estimate the cost to the country’s economy from increased journey times caused by the 20mph speed limit are anywhere between £2.7 billion and £8.9 billion.

Commons Leader Penny Mordaunt said having the 20mph limit as the default for so many roads was “crazy”.

There have also been reports of the new signs being defaced in areas including Conwy, Gwynedd, Newport, Torfaen, Wrexham and Flintshire.