The introduction of a 20mph speed limit on most residential roads across Wales from Sunday is proving one of the most controversial the Labour-run Welsh government has ever put in place. Welsh ministers argue it will save lives and lead to fewer injuries, save money for the NHS and make communities more pleasant places to live and work in. The Conservatives argue it will cost the Welsh economy billions of pounds with the Welsh shadow transport minister, Natasha Asghar, calling the rollout “madcap, ludicrous” and Penny Mordaunt, the leader of the House of Commons, attacking it as “absolutely insane”. The RAC warned drivers not to rely on satnavs on Sunday as not all maps will have been updated. The motoring group’s 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 satnav 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.” A petition against the policy, which was in Welsh Labour’s manifesto when the party matched its best-ever Senedd election result in 2021, has reached 70,000 signatures and new 20mph signs have been defaced across Wales. A poll for ITV found almost two-thirds of people were against it. The Welsh first minister, Mark Drakeford, has admitted that a “period of turbulence” will follow the introduction of the 20mph limit but said: “I’m also confident that once the policy is operating, people will see it is a sensible and progressive thing to do.” He said that if journey times were increased slightly but lives were saved it would be worthwhile. Why is Wales introducing the 20mph limit? The Welsh government claims the evidence from around the world is clear – decreasing speed limits could result in 40% fewer collisions and save up to 10 lives and prevent up to 2,000 injuries a year. It says streets will be safer, more people will be encouraged to walk or cycle, reducing the number of polluting cars on the roads. The safety charity, Brake, says the 20mph limit will save lives and create happier and healthier communities. Which roads will be affected? The law changes the default speed limited on restricted roads. These are usually residential or busy pedestrian streets with streetlights. Most roads that are set at 30mph will change to 20mph. But not all – local authorities will be able to choose which roads should remain at 30. Roads affected are shown on a Welsh government map. Opponents say the scheme will cost the Welsh economy £4.5bn. Is that true? The figure comes from a Welsh government report, which makes it awkward for Labour. The cost is for a 30-year period and the government now says it may not be accurate as it takes into account the impact of every single journey – even if it is just a trip to, say, the local park. It prefers to highlight the cost of introducing 20mph – £32m. It says the policy could save the NHS £92m every year so the initial outlay will swiftly be covered. Has the scheme been trialled? Eight trial areas were set up, with mixed results. In the village of St Brides Major in south Wales, residents seem largely impressed. The percentage of people travelling at or below 24mph has increased from 23% to 45%, Transport for Wales found. But there has been a vociferous campaign against it in another trial area, Buckley, north Wales, where drivers have tied red ribbons to cars to signal opposition and opponents have been defacing 20mph signs. How will it be enforced? Primarily by the police, just like any other speed limit. Police say the response will be proportionate as motorists get used to the change and those who engage with officers will not be penalised. However, those caught by speed cameras are likely to get tickets. Controversially, firefighters will also be involved but the government says this is the service’s road safety team, rather than those who would be called out to emergencies. Privately, some members of the emergency services have expressed concerns that their response times might be affected, although the government argues that the 20mph limit could make it easier for them to get to calls. The RAC said compliance with 20mph limits was “quite poor” and it would be “more effective to target areas where they are most needed” such as on residential roads or in areas where there is high footfall. Where else have 20mph speed limits been introduced? Spain introduced a 30kph (19mph) for single carriageways in urban areas in 2021. Figures from 2022, show that the number of pedestrians killed in these areas reduced by 13% compared with pre-pandemic figures. The Welsh government expects other UK countries to follow its lead. Many UK cities and towns have 20mph zones. Ironically, despite Mordaunt’s comments, the city she represents, Portsmouth, says it was the first British city to implement a 20mph speed limit on almost all residential roads to reduce road casualties and protect pedestrians and cyclists. The UK government says it has no plans to follow suit in England.