Fog is air humidity condensed into tiny water drops. It is often found in flat areas, near water courses and in the absence of wind. In the air layer above the ground – around 20 cm – fog is much thinner or even disappears. It is here that the fog lamp light beam cuts through: for this reason fog lamps must be mounted low and project little light upwards.
Unfortunately light tends to be absorbed and dispersed in fog (turning on your headlamps only generates a dangerous “light wall”), dampening colour contrast and differences and making objects less visible. For this reason, one should not rely too much on the front lamps: they do serve to improve visibility of the lines marking the side edge of the carriageway or the lane, but they might prove inadequate to perceive obstacles. Fog also makes it more difficult to guess the speed of the vehicles ahead.
Every year hundreds of fog-related accidents take place, often resulting in huge pile-ups or cars driving off the road, crashing against trees, poles, parapets or involved in head-on collisions. In fog your safety depends both on what you do, and most importantly on what others do (and should not be doing). Some important tips: decrease your speed and make sure you are visible. Speed should be kept within the limits set by the law based on the visibility of objects that do not emit light.
You should be able to notice obstacles in time and to stop your vehicle safely. Remember that the Highway Code sets the speed limit in case of fog at 50 km/h on all Italian motorways. In fog, what matters is that others see you.
Even in daylight, turn on your dim headlights and your fog lamps, if you have them. Turn on your rear fog lights.
Read the Variable Message Panels and follow indications with care, and comply with the speed limits indicated. Listen to the radio to receive updates and information.
Focus on the road and on your driving. If you drive for a long stretch in thick fog with no traffic, the eye – in the absence of stimuli – tends to focus on a “resting” distance of around three meters: KEEP YOUR EYESIGHT FOCUSED FARTHER AHEAD.
Do not make the mistake of following the taillights of a car ahead if traveling at a speed that is higher than the recommended speed: you have no way of knowing with certainty that that driver can see better than you do.