Car usage is also growing among older people, according to the first study to look at the relationship between demographics and the amount of time people spend in cars.

The study, published in the journal Preventive Medicine, shows that about 16 to 18 per cent of Sydney men spend more than two hours a day in their car, either as drivers or passengers, compared with about 10 to 12 per cent of women.

For men, the rate has remained steady for the past decade. But the number of women, particularly over the age of 35, spending long hours in the car has been increasing over the past 10 years.

For women between the ages of 55 and 64, for instance, the proportion spending more than two hours in their car has risen from 7 to 12 per cent.

The study, by five researchers at universities and government departments across Australia, uses information from Sydney's Greater Metropolitan Area Household Travel Survey.

It suggests that a reason for greater driving time among women might be rising female participation in the labour force.

But it also notes that long hours spent behind the wheel typically attract health risks. A study in 2004 showed every additional hour in a car was linked to a 6 per cent increase in the rate of obesity.

A separate study that tracked men aged over 21 showed those who sat in a car for more than 10 hours a day had a 50 per cent greater chance of heart illness than those spending less than four hours a week in a car.

Until recently, Sue Day, a credit manager for a food company, would drive regularly from her home in south Penrith to her work in Alexandria, leaving home at 5.30am to be at her desk by 8am.

Sometimes she took a train and a bus, but often that was not an option.

''It was 2½ hours in a car, highly stressful, and it was the biggest waste of my time,'' said Ms Day, who is also an advocate for public transport.

''My husband noticed my obscenities would make him blush and he's a tradie in the building industry,'' she said. ''Your personality changes; my blood pressure went up and the worst thing, you start putting on weight.''

Ms Day preferred days she could catch the train.

''I would have to walk to get the train, so I was getting exercise, I was on my laptop, on my phone, and I would get off at Redfern and walk and get a bus. It was stress-free, I was exercised and up to speed with everything I needed to know.''

Bindi Paag, an occupational therapist from Mount Victoria in the Blue Mountains, has a different perspective.

''I don't mind - I like it,'' Ms Paag said of her regular car trips across Sydney and others as far as Bathurst.

''The only issue that I find in regards to health is finding something healthy to get for lunch, because generally when you are driving you'll stop at McDonald's, just because there's a drive-through,'' Ms Paag said.

''The way the public transport system is I would rather be in a car.''