It’s official: Drinking makes you ‘blind’

Scientists at Spain's University of Granada have shown that drinking alcohol impairs night vision by intensifying people's perception of haloes around light sources like car headlamps.

It's official: Drinking makes you 'blind'
The volume of tears was found to be reduced by alcohol consumption, with potentially serious consequences for night-time driving. Photo of car driving in tunnel:

In the new study, published this week in the Journal of Opthalmology, researchers noted that night-vision disturbances of the 67 people they tested increased after drinking a "quality" wine, with effects similar to those caused by ageing.

Contrast sensitivity and the ability to discriminate details under low light conditions were found to be reduced.

The team lead by José Castro found that alcohol also caused actual physical changes in the eye.

Tears are shaped by a liquid film which was affected by the presence of alcohol (ethanol) in the tears after heavy drinking.

The scientists speculated that ethanol in the tear film makes it easier for water to evaporate, reducing the tear's volume, creating 'scattering' and optical aberrations such as haloes and starbursts around light sources such as car headlights and traffic signals.

They found optical aberrations occurred in subjects with breath alcohol above the Spanish legal limit of 0.25mg/l.

"These results could be taken into consideration in such fields as driving, where it is of vital importance to evaluate the visual abilities of the subject," the researchers said.

This is important "especially under night-time conditions, where physiological changes and visual alterations occur".

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How misusing fog lights when driving in Spain can cost you

With the cold weather in Spain often comes foggy days, rain and snowfall in the mountainous areas, all reducing visibility while driving, but did you know that you can actually be fined for using your lights incorrectly?

How misusing fog lights when driving in Spain can cost you

When fog appears and visibility is reduced, Spain’s General Directorate of Traffic (DGT), states that your front fog lights and rear fog light will help you to both see better and be seen by other drivers.  

But, they warn that you should be careful because if you use them incorrectly you can momentarily blind other drivers and could be at risk of being fined.  

Fog lights should only be used to see and be seen in low visibility conditions and using them in other types of circumstances could lead to a fine of €200.

Front fog lights

Front fog lights are not mandatory and are not a feature on all vehicles. If your car has them, you must make sure they are only used in conditions where your visibility has been significantly reduced. They may be used on their own or in conjunction with short-range lights.  

You can also use them at night on narrow windy roads, less than 6.5 metres wide, however, you must be careful when using them in this situation as they can be reflected in your rear-view mirrors and temporarily blind you.  

Rear fog lights

Rear fog lights are bright red lights that make the vehicle more visible from behind and are more intense than normal tail lights. Cars can have one on the left or in the center; or two, on the outer edges. 

It is mandatory for all cars to use these in unfavorable conditions, which include very thick fog, very heavy rain or lots of snowfall. You must make sure to turn them off in traffic jams or when there are lots of other vehicles around, however, so as not to blind the drivers behind you. 

Full headlight beams

The DGT warns that even though you may want to put your full-beam headlights in the fog, it can actually be counterproductive, as the beams will bounce off the fog and back at you, causing your visibility to decrease even more.  

Tips for driving in the fog: 

According to the DGT, the majority of fatal traffic accidents in the fog are caused by human error that almost always have to do with unforeseen and unnecessary braking, stopping on the hard shoulder without proper signs, or not keeping a safe distance between you and other vehicles. They have put together a list of tips for driving in low-visibility conditions. 

Pay attention to road markings
Make sure to pay attention to the longitudinal marks on the ground and stick to them, this will help to keep your car centered in the correct lane.

Reduce speed
When there is fog on the road, you must slow down so that it’s easier to stop when you need to quickly. At 50 km/h when the ground is wet a car cannot stop within 30 metres. If the fog is very dense, it is better to leave the road and park somewhere safe, while you wait for it to clear up.

Avoid overtaking
The DGT advises that is best to avoid overtaking on dual carriageways or motorways with dense traffic when it’s foggy and to keep a greater safety distance than normal.

Don’t stop on the hard shoulder
Stopping on the hard shoulder when there’s fog is a bad idea because it can be very dangerous. In fact, the DGT says that stopping on the hard shoulder should be avoided, even on sunny days, unless your car breaks down and it’s absolutely necessary. In this case, all passengers should exit the vehicle and stand on the other side of the guardrail. You must also make sure the hazard lights are on.