While we all normally pay attention to major health problems that can affect our driving skills, we pay less attention to the host of mundane illnesses that affect many drivers and can increase the risk of having a crash.
A cold, a headache, tiredness, stress, indigestion, a stiff neck, a bad back, stiff joints - the list is endless.
Cold or 'flu sufferers at the wheel - for example - may pose a risk to themselves and other road users at this time of year.
A sudden burst of sneezing can often cause a driver to lose concentration and vision for a considerable distance.
This means that if a 'flu sufferer has a bout of eight or nine sneezes when travelling at 120 km/h on a motorway, vision could be lost for up to 700 metres.
If you've had your 'flu shots or are otherwise healthy, remember that the driver in front or behind you may be about to have a bout of sneezing and be affected for some considerable distance.
There are some simple things that a driver can to if he or she is having a bad 'flu day.
Obviously, if it's really bad, you shouldn't drive at all. If your journey is really necessary, try to get someone else to do the driving.
Also very important is checking that any medication you take is suitable to use if you're going to drive - many 'flu remedies cause drowsiness so, as with any medication, check the label, or ask when buying it.