Everyone knows that driving with too much alcohol in your system is illegal and endangers lives. But not everyone knows that if you drive whilst dehydrated, it can have the same affect on your driving ability as a couple of glasses of wine – scary stuff!


Despite most of us topping up our coolant, windscreen wash and oil before long journeys, not many people consider our own fluid levels.

Driving in a hot, stuffy car on a summer’s day will result in you losing significant amounts of water. Dehydration affects both your co-ordination and your concentration levels.

The main symptoms of dehydration are…


  • Losing focus
  • Drowsiness
  • A dry mouth
  • Dizziness/feeling light headed
  • Reduced reaction times
  • Cramping muscles

Loughborough University put some drivers through a series of tests on a driving simulator to examine how reaction times are affected by mild dehydration – and the results were shocking!

The drivers made two times the amount of minor errors when dehydrated as they did when hydrated, that is the same number as those who have been driving whilst over the drink limit.

This was due to alertness and concentration being massively reduced. The drivers were making mistakes such as braking too early or too late and drifting out of lane.

The Department for Transport states that the biggest cause of road accidents in the UK is driver error, 68% of crashes are as a result of this.

Staying Safe

To avoid the dangers of dehydration whilst driving try to stick to the recommended 2 litres of water a day, especially when the sun is out.

Ensure you drink plenty of fluids before getting in the car, even if it means you need a toilet break en route!

If you ever feel tired whilst driving then stop for a drink containing caffeine or sugar to give you a boost or rest until you’ve recovered.

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