30 km/h zone

Reviews of formal studies in many countries have found that 20 mph zones and limits are effective in reducing accidents and injuries, traffic speed and volume.

The limited evidence from existing 30 km/h (20 mph) schemes shows marked reductions in deaths and casualties.

[18] Lyon has the wider 30 km/h zone, with an area of 500 hectares (or 5 square kilometers) covering 87 km of road lanes.

[22] Since 30 August 2021, Paris has 30 km/h zone on most of the city except périphérique, boulevards des Maréchaux and few other streets.

[24] In January 2024 Bologna enacted 30 km/h as the default maximum speed on 70% of its streets, covering around 90% of the city population.

[28] The council of the mostly-rural Scottish Borders, UK, tried a 20 mph speed limit in 97 villages and towns from October 2020.

[29] In Wales in September 2023, after supportive reviews of the literature,[30] commitment in the manifesto of the ruling Welsh Labour party, after some years of successful pilot studies,[31] extensive consultation,[32][33] supportive opinion polls,[34][35] and further consultation by local councils, a 20mph limit was introduced as a default for residential roads.

Public Health Wales predicted that this would save up to ten lives and about two thousand serious injuries per year.

[42] However, in 2023, the leader of the Welsh Conservatives began to claim that the policy was for a "blanket" 20mph limit, and the issue became the "most toxic" in years.

[38] The Senedd's petition site recorded over 450,000 signatures to a request for the policy of "reducing to 20mph EVERWHERE" to be stopped.

[43] A motion of no confidence in Lee Waters, Deputy Climate Change Minister, was backed only by Conservatives and was defeated in the Senedd.

[44] In the week after implementation, analysis of in-vehicle GPS data showed that traffic speeds on urban roads in Wales reduced by 2.9mph.

Half of the drivers were sticking to the new limit and there was a significant reduction in the length of roads where speeds are well above 24 miles per hour.