The decision on cycling depends on a number of risks and benefits. The biggest problem with cycling, says the London Cycling Campaign, is what happens when you're not on the bicycle. Of the 6 million bikes in the UK that are used regularly, 1 per cent - 60,000 bikes - are stolen each year.
But let's assume that you feel that your bicycle lock is sufficient, or your bicycle sufficiently grotty not to attract a thief's attention. The next statistical balancing act is: will the chances of extending your life through exercise outweigh the risks of being hurt, poisoned by pollution, or killed?
On this, the answers are more definitive. On average, about 200 cyclists die on British roads each year (of which 20 are killed on London's streets). If you are one of the 1 million people who cycle to work each day, therefore, your chances of death en route to your desk are slim.
On the plus side, if you do three hours' cycling each week - equivalent to a 20-minute journey (on flat ground, about five miles) five days a week - then you halve your chances of having a heart attack and reduce your chances of heart disease by 10 per cent.
But given all the warnings about air pollution, aren't cyclists just making things worse for themselves rather than better by exercising amid the exhausts?
No, says Dr Mayer Hillman, senior fellow emeritus at the Policy Studies Institute. "All the evidence suggests that it's the drivers who are worse off. The air that they breathe comes in to the car through the intake vents at the front; and that has come out of the exhaust of the vehicle in front. If you're on a bike or walking along the pavement, you're breathing the rest of the urban air."
Dr Chris Jarvis, medical officer for the British Cycling Federation, agrees. "You have to be doing yourself some good in terms of cardiovascular fitness."
In fact, says Dr Jarvis, "People who cycle tend to have healthier lifestyles. They don't smoke, they're more careful about what they eat, they're less likely to be seriously overweight."
Finally, despite the current heatwave, you do have to ask yourself one last question about luck: will it rain? "Statistically, if you go by the same route at the same time each day, you will only get seriously wet 12 times a year in any part of Britain," says Ms Curtis. That's in a working year of around 200 working days.
However, some government ministers clearly don't reckon that luck is on their side. Steven Norris, the junior transport minister, was still using his car even on the hottest days last week.Reuse content