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Dangers of driving while dehydrated

Dehydration leading to impaired driving can happen to the following types of drivers:

  • Drivers caught in traffic jams or snow storms that haven’t got liquids on board
  • Commercial heavy vehicle drivers who don’t want to stop unnecessarily because of schedules that need to be kept
  • Drivers of farm machinery and earthmoving machinery that doesn’t have air conditioning or is open to the elements when it’s hot – this includes quad bikes
  • Drivers of machinery that is difficult to get into and out of, such as mining trucks and larger cranes, where stopping to go to the toilet is both time-consuming and costly to the company
  • Approved Driving Instructors who are driving from client to client all day with little chance to have a break
  • Motorcycle and scooter riders wearing full protective gear (helmet, jacket, trousers, boots, gloves and any body armour), especially if the weather is hot and the traffic is slow (i.e. less ventilation and cooling from the wind)
  • Taxi drivers and bus drivers whose shifts are long and when it’s difficult for them to leave their vehicle.

Most of us only think about dehydration when it’s hot (if at all), but you can be dehydrated any time of the year if you don’t take on enough liquid. Sure, long journeys on a hot summer’s day will make you more prone to dehydration, but you can be dehydrated because of alcohol consumption the night before, or just generally not drinking enough.

Bear in mind also that your passengers can become dehydrated, too. Children might not express that they need a drink, and older people have less sensitivity to thirst. Passengers might not want to ask you to stop if you are in a hurry or on a schedule.

This lack of sensitivity to thirst is one of the things that can make driving more dangerous for the elderly. If you keep ignoring your thirst, your body will stop telling you that it’s thirsty. In extreme cases your blood platelets start to clump together and the blood becomes thick enough that the heart can’t pump it effectively.

Effects of dehydration on driving

When you are too dehydrated certain functions in your body start to become less effective. At the point at which you feel thirsty you can be around 250ml or one glass of liquid down on your requirements. At this point your driving shouldn’t be too impaired, but if you ignore it, you will start experiencing a slowdown in cognitive (brain) function. You could get one or more of the following symptoms

  • Dizziness/lightheadedness
  • Tiredness
  • Headache
  • Dry mouth, eyes and lips
  • Bad breath (halitosis)
  • Hunger

The first three increase your risk of having an accident. Many people suffer from frequent headaches and treat them with painkillers and a glass of water whereas all they needed was the glass of water to correct a dehydration problem. They incorrectly attribute the lessening of the headache to the painkillers (note: this doesn’t apply to all headaches, so if they persist, see your doctor).

To alleviate the symptoms of dehydration is a simple two-step process:

  1. Pull over somewhere safe (and preferably shady)
  2. Drink fluids or eat food with a high water content and low protein content (protein takes water to digest).

It’s that simple. Cucumber contains 96% water, and the majority of fruit (with the exception of bananas) contains at least 85% water. Eating water-rich food will also help you replace minerals and vitamins lost through sweating and urinating.

Hunger is sometimes a symptom for dehydration whereby the body is just looking for any source of liquid.

The average male should be drinking around two litres (3.5 pints) of water a day, plus getting another 250-500ml of water from food. Females usually require slightly less, depending on size.

Advanced symptoms

The next stage of symptoms will see your blood get thicker (increases risk of all kinds of emergency medical situations like stroke, heart attack, etc), low blood pressure, rapid heartbeat, symptoms of fever, irritability and confusion. Leave it any longer and you will descend into delirium and unconsciousness. At this stage (whereby you do have to be quite dehydrated), and can sometimes be too far for you to just drink liquid to reverse it and you may need to be put on an intravenous drip in hospital.

Testing for dehydration

The single most reliable test (and the cheapest) is to check the colour of your urine. Excluding any discolouration from taking a vitamin tablet, your urine should be almost clear. If it’s yellow, you are dehydrated. Simple.

Avoiding dehydration when driving

The most at-risk time for dehydration is driving in the morning just after you have woken up. This is because you will have been eight hours without a significant drink (while you were sleeping), and many people don’t have a huge amount of liquid for breakfast. If you have a salty, greasy, protein-rich breakfast, this will use up your available liquid much more quickly as protein and fat require more water to digest than carbohydrates.

If you know  you will be driving a long distance, or if there’s a risk that you might be held up due to traffic or weather, take liquid with you. Water is the best. Tea and coffee are fine as long as you don’t exceed three to four cups – any more than this and the caffeine starts acting as a diuretic which makes you lose water. Fruit juice is fine, but it’s not recommended to sip fruit juice because of the acidic nature of it on your teeth. Soft drinks are bad for you and the sugar, along with your sedentary day driving, could contribute to weight gain. Stay away from alcohol for obvious reasons. If the liquid is in a sipper bottle, that is the most convenient.

Also take fruit with you. Some fruit is able to be eaten without too much distraction while you are driving, e.g. grapes, strawberries and apples; other fruit is messier, e.g. pears, melon and oranges. Ideally you should stop to eat so that your focus isn’t taken away from the road. You can pre-peel satsumas and tangerines before you leave, and put them in a contain that’s easy to open.

The best prevention for dehydration is early recognition that you are thirsty. Having the equivalent of a glass of water at that time will keep your mind sharp and your driving as good as it can be.

Darren has owned several companies in the automotive, advertising and education industries. He has run driving theory educational websites since 2010.

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Posted in Advice, Car, Driving Instructors, Heavy Vehicle, Motorbike, Passenger Vehicle
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