Large groups of us used to kick a ball around, or race our bikes around the block in 1960s and 70s Knowle.

Kids playing in the street is a much rarer sight now, not least because our roads are much busier.

The current default speed limit of 30mph in areas where people live was set in 1934 when there were 1.5 million motor vehicles. Now there is a massive 33 million. Road traffic in the UK is the single biggest cause of premature deaths for boys and the second biggest cause for girls aged between five and 15. Every year in Bristol, 500 people are killed or seriously injured on the roads, the burden falling hardest on the poorest, with 24 of every 100 child pedestrian casualties being in the most deprived neighbourhoods, compared to one in 100 in the least deprived.

At 20mph a pedestrian knocked over stands a 90 per cent chance of surviving. At 40mph they stand a 90 per cent chance of dying. Clearly, 20mph in residential areas is fast enough, and the new 20's Plenty For Us initiative in the area is aiming to make this a reality.

Compare our residential street speed limit of 30mph with the speed limit in northern European towns. Our limit is 60 per cent higher than the 18.5 mph (30 kph) limits that they have for streets where people live. No wonder, perhaps, that 92 per cent of pedestrian deaths are on urban roads in the UK, and at 21 per cent we have a higher proportion of pedestrian deaths on the roads than any of our European neighbours.

In Hilden, Germany, the setting of its 18.5 mph (30 kph) limit in the early 1990s was the foundation of encouraging cycling and walking. In fact, now 23 per cent of in-town trips are made by children and adults using bikes instead of cars.

Something has to change to bring us into the 21st century. Adults lead more sedentary lives, in part, because they spend more time in their cars. Children lead less active lives, in part, because we worry about the dangers posed by road traffic.

The growth of physically inactive lifestyles in industrialised countries has led to what many are calling a major public health crisis. Preventable illnesses associated with inactivity and obesity include stroke, heart attack, certain cancers, diabetes and depression.

About 40 per cent of people in the UK report being bothered by noise from traffic, nearly double the figure from the 1970s. Children living near busy roads suffer significantly higher rates of asthma and West of England Partnership figures show that more than 100,000 Bristolians live in areas where air quality is considered to be potentially damaging to health.

Cars travelling too fast in residential areas have helped to create social degradation. Neighbours who live across the road from each other don't talk to each as often as they used to when I was kicking a ball about with mates, because a gulf is created by cars speeding past. As far back as 1969, Prof David Appleyard found that the idea of "community" was eroded on San Francisco streets with busier traffic.

A study by Kevin Leyden in 2003 found that people "living in walkable, mixed-use neighbourhoods were more likely to know their neighbours, participate politically, trust others and be socially engaged, compared with those living in car-oriented suburbs".

Research on Bristol's streets by Josh Hart at the University of the West of England showed that motor vehicle traffic is responsible for a considerable deterioration in residential community, measured by an average number of social contacts, extent of perceived "home territory", and reported street-based social activity. Several studies show that people whose homes had windows facing busy streets were more often depressed.

The campaign group 20's Plenty For Us was formed to work for the implementation of 20mph as the default speed limit on residential roads in the UK, in place of 30mph. The balance is shifting towards roads and streets as public spaces for people rather than just motors – safer, cleaner, healthier and more civil. Quality of life would be better, with less noise, lower pollution, and greater child mobility, walking, cycling and talking encouraged, so a better general wellbeing.

The Bristol 20's Plenty group was launched recently to help build improved quality of life in local communities. There are 40 neighbourhood champions already in place, including myself in Knowle, and the target is 100 champions.

To be involved either as a champion yourself, or as part of a team, email champions@20splentyforbristol.org.uk. or check out the national and local websites for up-to-date news, reports, articles, action packs, support and resources.

Glenn Vowles can be contacted at knowle@20splentyforus.org.uk. His blog is at: vowlesthegreen. blogspot.com

For further information, go to:www.20splentyforus.org.uk or www.20splentyforbristol.org.uk