In the independent tests – which measured physiological stress markers in participants' saliva – it was revealed that women suffered an 8.7% increase in stress from driving in traffic, whilst men suffered a staggering increase of 60%.

More worryingly, in the same tests 67% of women and 50% of men reported not feeling stressed 20 minutes after driving in traffic, when physiologically they were.

The research goes on to suggest that the effects of long-term exposure to stress chemicals include suppressed immune function, raised blood pressure and elevated blood sugar levels.

Health psychologist David Moxon who led the research said: 'These findings make good evolutionary sense. Men, in particular, show a strong acute physiological "fight or flight" response. The fact that they are not always aware of this could indicate that driving regularly in dense traffic could have a profound effect on their health.'

The research reveals there is a range of noticeable symptoms, although drivers may be oblivious to the effects. Physical symptoms include dizziness, breathlessness, muscular aches and even chest pains, while behavioural symptoms include agitation and erratic driving.

To deal with traffic-induced stress, drivers have developed a number of coping strategies. The survey reveals that 82% of drivers listen to music, whilst 21% talk to other passengers in order to pass the time and ease the tension.

TomTom is encouraging drivers to break free from traffic through its Break Free trade-in promotion, giving them up to 50 euros off a TomTom device with HD Traffic. Drivers can trade in any satnav – of any brand and any age – and benefit from TomTom HD Traffic, so they'll always know how long a journey will take. And if there is a quicker route, they'll get it immediately.

For more information about the Break Free promotion and the trade-in, visit www.tomtom.com/breakfreepromo