Speed limits of 20mph are being seen increasingly on residential streets, and they’re popular: recent Department of Transport research showed 73% of people are in favour. Campaigning from groups like 20’s Plenty for Us and Living Streets has paid off, with support growing significantly.

Slower speeds are necessary to reduce injuries. But even if 20mph limits can be properly enforced – a big question – would this be enough? Do they, alone, create pleasant, liveable neighbourhoods, where lots of people will choose to walk or cycle? Do we want to see a steady stream of traffic in residential streets, even travelling at 20mph, or should our goals be more radical?

Recent guidance from Royal Society for the Prevention of Accidents (Rospa) and Public Health England states: “There is a road safety argument for reducing [motor] traffic volume, and there is also the potential to do so.” Slow-moving, large vehicles like lorries and buses can still kill because of their sheer weight.

And it’s not just large vehicles that are the problem. As Rospa points out, each car journey creates additional risk to others, even if lower speeds reduce that risk.

More cars on residential streets also means places which are less human-friendly, particularly for the old and the young, who struggle to navigate busy streets on foot and often have lower access to cars.

A recent study found the dominance of cars on residential roads has substantially damaged young people’s quality of life in urban and rural areas.

My colleagues at the Policy Studies Institute have studied the long-term decline in children’s independent mobility, including through cycling. They concluded that improving road safety and reducing car dependency is key to winning back children’s freedom to roam.

My own research found many parents might trust their children to cycle, but don’t trust drivers to take care around them. This is backed up by experience. Often parents have suffered scary incidents on routes which were chosen because they should be more quiet than main roads but are too often used as rat runs.

As one parent explained:

I had to push my child off her bike between parked cars in order to stop us both being run over by a driver coming at speed in the opposite direction.

Increasingly, research into such ‘near miss’ incidents show they can have a substantial impact on the choices people make.

They are common: 1%-2% of all overtakes give a cyclist under 50cm of clearance, according to a recent study. In residential streets carrying thousands of vehicles per day, that means regular cyclists experiencing terrifying close passes on a weekly basis. No wonder people don’t want to let their children ride bikes – or even walk across the road – in such conditions.

And if there was no rat running, many local streets could be extremely quiet. DfT trip rate statistics allow us to estimate how much traffic there might be on residential roads without people using them as short cuts. Even including deliveries and visitors we’re generally talking about a few hundred cars a day or fewer. Such streets could be places where cars really are guests, and children again walk and cycle freely.

Controlling this by putting gates to prevent through traffic, can be controversial.

One reason is that we’ve got used to being able to drive wherever we please, even if it means our children can no longer leave the house alone. But there’s also concern that cutting traffic volumes in residential streets will displace the problem elsewhere, maybe increase safety issues overall.

New analysis of road injury data helps allay some fears, suggesting that moving traffic from minor to major roads can reduce pedestrian injuries. In urban areas, driving along a minor road causes around 50% more risk to pedestrians than driving the same distance along an A road.

In 2014, motor vehicles injured 7,179 pedestrians on urban A roads and 14,168 pedestrians on minor urban roads. The distances driven on the two road types are 49.3bn and 64.8bn vehicle miles respectively.

So, stopping rat-running can reduce pedestrian injuries. Making motorists use major roads won’t even necessarily mean more miles driven, because rat runs are generally chosen to avoid congestion rather than reduce mileage. Often that doesn’t even cut a journey time.

What about air pollution? Air quality and active travel expert Dr Audrey de Nazelle said:

Giving active travellers a network of streets away from motor traffic helps them minimise exposure to air pollution, important because their inhalation rate is higher than for passive modes. Cutting traffic on the residential roads will improve air quality on these streets. Will it increase traffic and hence air pollution on major roads in the surrounding areas? Probably a little – but if the programme is ambitious and many residential streets reduce vehicular access, there will be overall less motor traffic in the area, so improvements in air quality overall.

Encouragingly, research has found that reducing space for traffic often reduces traffic volumes overall in an area, partly because creating more pleasant streets means people are more likely to walk and cycle for shorter trips.

On the main roads, there’s more we should be doing to improve safety and quality of life: from wider pavements, more pedestrian crossings, cycle tracks and tree planting, to 20mph limits and air quality management areas, and broader policy measures to cut the use of diesel engines. Many of these policies will be popular: there is high support for cycle tracks on main roads, for example. Along with this could and should involve ways to return residential streets to their residents, walking or cycling if they choose.

Dr Rachel Aldred is senior lecturer in transport at Westminster University, specialising in sustainable travel.