Setting the default speed limit at 20mph in residential roads in Wales will save £100m in the first year alone as deaths and injuries are reduced, according to research.
The move, a first in the UK, will save more than 100 lives over a decade, the research claims, though a second study has found many people are concerned the limit will be very difficult to enforce and do not believe drivers will respect it.
The Labour-led government is introducing the 20mph speed limit scheme for many roads in residential and built-up areas across Wales in September 2023.
A blanket speed limit on all roads will not be applied but the legislation will make the default limit 20mph, leaving local authorities to engage with communities to decide which roads should remain at 30mph.
Some opposition politicians and motorists have opposed the policy, claiming it will lead to greater congestion, confusion and not be enforceable.
The new research, from the Transport Research Institute (TRI) at Edinburgh Napier University in conjunction with Public Health Wales, says the direct costs of introducing the ban have been estimated at £32m. But it says the savings that will be made in the first year alone are more than three times this because so much less money will be spent on dealing with the aftermath of accidents.
The report adds: “Evidence suggests that the health benefits of 20mph are far, far greater than casualty savings alone. They include increased physical activity, and therefore less obesity, less stress and less anxiety, as well as other health benefits such as reduced noise and air pollution.
“We know from previous studies that 20mph encourages more walking and cycling and in doing so improves cardiorespiratory health, as well as reducing stress and anxiety, thereby improving mental health. With more walking and cycling comes less car use, improving air quality and therefore improving health.”
The Welsh government also published an independent public attitude survey, conducted by Beaufort Research, showing that most people interviewed supported a 20mph speed limit where they lived.
One in three said 20mph speed limits would also make them more likely to walk more, while about one in five said that they would be more likely to cycle more. Support is strongest among parents, women and those in the middle age range while men, while younger people and over 65s are less likely to support 20mph speed limits.
The survey indicates there is a great deal of scepticism over whether driver behaviour will change: two in three Welsh adults believed that most drivers would not stick to a 20mph limit.
The deputy minister for climate change, Lee Waters, said: “The evidence from around the world is very clear – reducing speed limits reduces collisions and saves lives.
“Slower speeds also create a safer and more welcoming environment, giving people the confidence to walk and cycle more, which will help to improve our health and wellbeing and help to improve the environment. As with any change we know it will take time for people to adapt.”
More than 45,000 people have signed a petition against the move and the Welsh Conservatives have called it unworkable.
Natasha Asghar, the Welsh Conservative shadow transport minister, said: “Labour ministers need to stop imposing dogmatic and restrictive measures on road users in Wales and focus on making sure Wales has a public transport system fit for the 21st century.”