Three in 10 children in England aged two to 15 are now overweight or obese, and the figures are similar across the UK. The World Health Organisation recently warned three quarters of men and two thirds of women in the UK will be overweight in 15 years' time if lifestyles do not change. Britain is teetering on the precipice of an obesity epidemic that could deliver the final knock-out blow to our faltering NHS.

We've all heard the obesity doom-mongering many times before, but what to do about it? Every public health initiative aimed at getting people to eat well and exercise seems doomed to failure. The only way many of us will live healthier lives is if we do so without realising it – if it is built into our everyday routine. The remedy for this crisis is to be found not in the gym, nor the organic food store, but on the streets.

Our parents' generation got much of the exercise they needed to be healthy simply by moving from place to place not encased in a wheeled metal box. And they started early – in 1971, 80% of seven to eight year olds walked to school independently. Active travel became habitual. That's why getting more kids walking and cycling as part of their everyday routine is vital, and why 100,000 children across the UK are kick-starting a love of walking by taking part in Brake's Giant Walk today.

However, when it comes to letting their own children walk and cycle to school, parents today are in a quandary. Only a quarter of them think the route between their home and their school is safe enough for their children to walk or cycle unsupervised. The reason: traffic danger. Road safety concerns top the list of factors stopping parents letting their kids walk or cycle, with 42% citing high volumes of fast traffic.

At the same time, the finding that only a quarter of parents put the decision to drive their kids down to distance or time, and only one in 12 to convenience, leaves the argument that it just isn't practical for most children to walk or cycle to school dead in the water.

However – and here's the catch 22 – by attempting to protect their children from unsafe roads by driving them to school, parents are contributing to the problem. The mere fact of so many vehicles trying to cram onto the same roads at the same time is enough to create more congestion and more traffic danger. The problem gets worse when the parents in question don't drive responsibly – one in eight surveyed by Brake admitted talking on a mobile phone or speeding on the school run.

Walking or cycling in this scenario takes courage, and letting your children do so might even be considered negligent. We can't insist parents take a leap of faith, so what's to be done? If we again listen to the parents themselves, more segregated walking and cycling routes and safe crossing points would help – they ask nobody to put themselves in harm's way.

If we can get more people walking and cycling – to school, work and play – on segregated, protected routes, then it necessarily reduces the burden of cars on the road. Maybe then, with the roads more clear – and limited to 20mph – we could reclaim them for all types of user to share, and we'd find we no longer needed quite so many segregated routes after all.

Brake campaigns for a 20mph urban default through the GO 20 campaign and backs a long-term walking and cycling investment strategy as part of the Infrastructure Bill.

Ed Morrow

Former campaigns and communications officer at Brake, the road safety charity