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The Hidden Dangers of Driving Dehydrated

Recently the UK has already experienced some of the hottest weather in over 30 years, and with it came the usual onslaught of warnings relating to driving, personal safety and health.

The team at Safedrive discuss what happens when you get behind the wheel of a vehicle, having not drunk enough water.

Driving dehydrated

Scientists at Loughborough University carried out a number of tests on drivers who were suffering from some level of dehydration. Shockingly, what they found was that most of these drivers made the same number of mistakes while dehydrated as the average drunk driver.

An average adult requires three to four litres of water daily just to function, more in hot weather. The study found that when drivers had a fluid deficit of 4% or more there was a significant increase in both body temperature and breathing rates, and they were considerably more likely to suffer from headaches and drowsiness.

All that considered, it makes sense to conclude that drivers put themselves at risk by not having enough fluids.

Why is this so important?

Any business should always be looking to reduce on-road risk. The ultimate goal is to identify areas of risk before they present themselves and actively work to avoid them – so something as simple as ensuring drivers are well-hydrated is a small change that results in much safer driving.

It can sometimes be difficult to ensure that drivers are taking care of themselves properly. A busy schedule and the fact that they’re often on their own for long stretches means that it’s even more important to instil self-care into their working routine.

Driver error accounts for up to 68% of accidents in the UK – and 78% of those accidents are caused by drivers being distracted by something, whether it’s a ringing phone or the drowsiness that comes with fatigue or dehydration.

There’s also an undeniable financial aspect. Distracted or fatigued drivers are statistically far more likely to be involved in road traffic accidents, which can lead to points on their licence, sizable fines, and potential prison sentences - not to mention the cost of claims, legal fees and increased insurance premiums for the business.

How to reduce the risk of dehydration while driving

Always drink enough water. An adult will require, on average, 3.7 litres of water per day to remain healthy and active – in hot weather, this should be increased

Try to avoid driving during the hottest parts of the day. Between the hours of 12pm and 2pm, the sun is highest in the sky and considerably hotter. Wherever possible, try to avoid getting behind the wheel during this time.

Open your windows. Sitting behind glass on a hot day will only worsen the effects of dehydration. Even using air conditioning can only help to a point – so consider opening windows or a sunroof to allow ventilation throughout the vehicle.

Check your vehicle. It’s always important to have a well-maintained vehicle and safety checks never go amiss, but they’re particularly important during hot weather. In very hot weather road surfaces can soften and may cause more wear to your tyres; always make sure they have more than the legal minimum tread depth of 1.6mm so they can hold up. Keep your coolant levels topped up and ensure your windscreen and mirrors are clean, clear and undamaged to avoid worsening potential glare.

Don’t drive tired. Dehydration is known to mimic the effects of fatigue, as well as exacerbating them. You should always try to get 6-8 hours of sleep a night and never drive for more than two hours without a 15-minute break.

Take care of yourself. Never drive when unwell, fatigued or under the influence of drugs or alcohol. Don’t wear clothes that will restrict your movement or control of the vehicle (e.g. flip flops), and try to remain patient with other road users if you can.

Contact us today to discuss your driver training needs.

Safedrive are proud to offer a professional and industry-aware range of Fleet Risk Management services.

If you’re interested in Fleet Risk Management services, or you would like to ask us for more information, please contact us on 0344 892 1728, or email us directly at


Safedrive can help with any queries you may have about fleet risk and driver behaviour by drawing on our expertise in reducing driving hazards. Safedrive’s fleet risk solutions include in-vehicle assessments, driver license validation, in-car cameras, and telematic solutions.

About the author

For more than two decades, Sadie Lane, Safedrive Fleet Risk Manager, has been educating and facilitating businesses to better manage fleet risk, driver behaviour and driver attitude through a wide range of Safedrive’s services and solutions.


The information and any commentary contained within these updates are for general information purposes only and do not constitute legal or any other type of professional advice. Stallard Kane does not accept and, to the extent permitted by law, exclude liability to any person for any loss which may arise from relying upon or otherwise using the information contained in these blogs. If you have a particular query or issue, you are strongly advised to obtain specific, personal advice about your issue and not to rely solely on the information or comments in these updates.
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