Fleet managers should be encouraging employees to drink more water.

Water Wellpoint looked at the effect a lack of fluids has on driving performance and discovered it takes 1% dehydration by weight to impact on concentration by 12%.

If dehydration goes up to 2%, concentration drops by 20%, while motor speed which governs reaction times reduces by 15%.

Crucially for drivers, hand-eye co-ordination drops by 12%, while general efficiency falls by 18%.

“Fleet managers should make hydration a key message in their duty of care for staff, ensuring they stay safe out on the road,” said Colin Wilson, research scientist, Water Wellpoint.