The Heart Foundation says Aussie parents may be missing a chance to combat childhood obesity as its survey reveals a dramatic increase in the number of children travelling by car to and from school, with 63 per cent of parents saying their children travelled by car, mostly for safety reasons.

Australian children are now among the most ''cosseted'' and ''chauffeured'' in the world, says Dr Jan Garrard, an expert in health promotion at Deakin University.

Speaking to Brisbane Times, Dr Garrard said some of the dangers parents felt were not based on sound evidence.

''There's been an increase in parents' perceptions of the danger, including where a child is kidnapped in Portugal, the UK or the USA, suddenly everybody knows about it around the world. But you could argue the greatest risk is sitting at home eating chips because that will probably do them more harm in the long run,'' she said.

A 1970 study by the Australian Bureau of Statistics showed that 84 per cent of all students in primary school, high school, university and TAFE travelled by public transport, walking and cycling, with just 16 per cent using cars. The new study shows that 63 per cent are driven to and from school while active transport use has dropped dramatically.

While the ABS has stopped its regular surveys, the Heart Foundation's survey, which is co-sponsored by the Cycling Promotion Fund, gives a picture of how children are missing out on physical activities, the foundation says.

Heart Foundation says the current pattern helps explain why Australia has become one of the world's most obese nations.

The nationwide study of 1000 parents, which allowed them to nominate multiple transport modes, found 63 per cent said their children travelled by car, 25 per cent said walking, 21 per cent said public transport, 11 per cent said bikes and 3 per cent said other means.

Traffic worries were cited by 50 per cent, 44 per cent were concerned about intersections and crossings and 42 per cent named the speed of traffic as the reason they would not let children ride to school.

The chief executive of the Heart Foundation, Lyn Roberts, urged the government to respond to the threats that parents felt in order to provide a healthy exercise for the children.

''We urge all levels of government to invest to ensure the next generation is able to adopt healthy and active options for their daily trip to school,'' she said.

''Cycling to school is clearly something that children are able to do and parents want to encourage, but they're being let down by a lack of safe cycle paths. We're missing a huge opportunity to tackle childhood obesity, reduce carbon emissions and ease road congestion.''