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20 MPH Zone

  • Most of the UK’s larger cities have adopted 20mph for their residential streets 
  • 28 million people in the UK live in places where 20mph is or will be the urban/village norm. 
  • Wales is about to implement a 20mph national default for residential roads. 
  • The General Assembly of the United Nations endorses 20mph or 30km/h speed limits where people mix with motor vehicles, unless strong evidence exists that higher speeds are safe. 

There are many advantages to 20mph zones in the UK. Here are some of the most notable: 

  • Improved road safety: 20mph zones have been shown to reduce the number of road accidents, especially those involving pedestrians and cyclists. A study by the University of York found that 20mph zones could reduce the number of road deaths by up to 40%. 
  • Increased physical activity: 20mph zones make it safer for people to walk and cycle, which can help to improve their physical health. A study by the University of Westminster found that people living in 20mph zones were more likely to walk or cycle for transport than those living in areas with higher speed limits. 
  • Reduced air pollution: 20mph zones can help to reduce air pollution, which is a major health hazard. A study by the University of Birmingham found that 20mph zones could reduce nitrogen dioxide levels by up to 15%. 
  • 30% Urban Fuel Savings Justify a Wide Area 20mph Speed Limit Policy: Reducing peak road speeds where people are saves energy and significant cash. New research from Future Transport shows fuel efficiency peaks with speed capped at 20mph. This “real life” model factors in stop/start urban traffic. Less acceleration saves precious resources as over twice as much energy is required to get to 30mph. Drivers get up to 10p per mile fuel saving without trips taking longer. That’s a 30% saving in urban fuel costs. 
  • Improved quality of life: 20mph zones can make streets feel calmer and inviting, which can improve the quality of life for everyone who lives or works in the area. A study by the University of East Anglia found that people living in 20mph zones reported feeling safer and more relaxed than those living in areas with higher speed limits. 

Overall, 20mph zones offer several benefits for road safety, physical activity, air quality, and quality of life. They are a cost-effective way to make our streets safer and more liveable for everyone. 

Further long term research is needed about the possibility that reduced speed limits can lead to an increase in pollutants.  Research at the moment seems to be a mixed bag.  A recent Welsh Government report looking at a number of other reports concluded: 

It would be incorrect to assume a 20mph speed restriction would be detrimental to ambient local air quality, as the effects on vehicle emissions are mixed; 

  • Driving styles (as characterised by the vehicle operating mode and distribution of cruise speeds) were found to be different on 20mph roads as compared to 30mph roads yet on residential streets with 30mph speed limits were often shown to have vehicle speed not exceeding 20mph. This was also true of heavily trafficked non-residential streets; 
  • Streets where traffic flow was more likely to be interrupted were shown to have higher emission rates. However, this was often the result of other traffic management infrastructure (pedestrian facilities and junctions); 
  • It is accepted that lower speed limits impacts on brake and tyre wear emissions resulted in lower demand for power at lower speed limits which is likely to be beneficial to emissions of this type. 
10 August 2023
Last Updated
10 August 2023