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The Case for Driving Hydration – Results

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The Case for Driving Hydration – Results

According to the Department of Transport, between October 2014 and September 2015, there were 23,700 killed or seriously injured (KSI) casualties in road traffic accidents.

Even more disturbing is that ‘driver error is by far the largest cause of these accidents, accounting for approximately 68% of all vehicle crashes in the UK.’

A sobering figure for all, it’s an especially grim statistic for transport managers and directors where injury or vehicle damage has a detrimental knock-on effect across all sectors of their business. Because of this, transport companies make every effort to reduce the rate of accidents wherever possible; from fitting cameras on vehicles, and training drivers (both on cabin safety and the harmful effects of sleep deprivation), to having a zero tolerance to alcohol and rewarding those drivers with a low claims frequency.

While these are all imperative measures, a study recently undertaken by Loughborough University, shows that there’s another very simple factor to add to any health and safety strategy to reduce driver errorensure drivers are properly hydrated.

In our three-part blog series, we provided an in-depth look at the hypothesis and methodology  behind the 2015 peer-reviewed Loughborough study which was funded in part by a grant from the European Hydration Institute (EHI) – the EHI did not directly contribute to the study design; the collection, analysis and interpretation of data or in the writing of the manuscript. In this, the last in the series, we focus on the results of the ground-breaking paper which underpin the need for the Driving Hydration solution.

To recap the hypothesis: studies show fluid loss impairs both physical and mental performance, the American College of Sports Medicine qualifies ‘mild hypohydration as body mass losses exceeding 1%’ and further studies show that dehydration ‘can result in impaired function, with changes in mood state and modest reductions in concentration, alertness and short-term memory reported.’ With this in mind it was ‘reasonable to assume that dehydrated drivers may be more susceptible to errors in judgement and/or the successful execution of motor skill.’

The aim of the study was therefore to explore the effects of mild hypohydration (dehydration) on performance during a prolonged, monotonous driving task where aspects of cognition relevant to driving were likely to be challenged.

To recap the methodology: eleven healthy young males, all experienced drivers with more than two years on a full licence and all driving for more than two hours per week, were asked to complete a two hour continuous drive in a driving simulator – the road had long straight sections followed by gradual bends; drivers were asked to remain within their lane unless overtaking slow moving vehicles. All men arrived at the trial well hydrated, and reported the same subjective feelings of thirst, throat dryness, hunger, alertness and ability to concentrate. As the task began however, the men were split into two trials: those further hydrated and those where fluid was restricted.

During the Hydrated Trial, participants continued to consume at least 2.5 litres of fluid spread evenly across the day. During the Fluid Restriction Trial, only 25% of the 2.5 litres of fluid (625ml of fluid) was permitted – the aim was to achieve a mild 1% drop in hydration levels over a 24hour period.

The results recorded were startling. While there was a progressive increase in the total number of driver errors observed across both trials, with significantly more incidents reported during the last 30 minutes than in the first 30 minutes, ’the frequency of driver error increased to a greater extent throughout the Fluid Restricted Trial’.

Dehydrated drivers made 101 driver errors compared to the 47 made by hydrated drivers, which means that a mildly dehydrated state of only 1% had dehydrated drivers make more than double the mistakes of their hydrated counterparts.

Sensations of thirst, along with dry mouth and headaches (in addition to the other well-established physiological consequences of hypohydration) are thought to directly produce a negative effect on mood state, leading to discomfort and distraction.

While ‘there was no change in thirst perception over the course of the Hydrated Trial, self-reported ratings of thirst increased by 107% throughout the Fluid Restricted Trial.’ Perceived ability to concentrate and levels of alertness were also significantly lower for dehydrated drivers by the end of the drive than compared to the hydrated drivers.

Important to note at this point is the level of dehydration and the age of the participants. The study aimed to achieve a mild dehydration level of only 1% – this is a level easily reproduced by individuals with limited access to fluids during a busy working day. Studies show it’s between 0.8-2% that we first begin to feel thirst, which is the body’s way of instructing us to replenish fluid levels. But also documented is that our ability to feel thirst reduces and continues to diminish after the age of 50; which means that the older we are, the more dehydrated we may be, without even being aware of it.

If one considers that the average age of the participant was 22 years, whereas the average age of an HGV driver (according to Skills for Logistics) is in fact 53 years, the results of the study with regards to driver error are actually conservative when compared to what they might have been had the trial group been older.

 To provide an even more startling context, the study goes on to draw a parallel between driving dehydrated and driving while under the influence of alcohol or sleep deprived:

‘A similar increase in driver error rate has been observed when driving following the ingestion of an alcoholic beverage resulting in a blood alcohol content of approximately 0.08% (the current UK legal driving limit), or while sleep deprived’.

Considering the findings of the study, it becomes clear how imperative it is to ensure drivers are adequately hydrated.

The Driving Hydration solution includes everything transport managers and directors need to both educate transport staff about the importance of proper hydration and supply them the practical steps to remain hydrated throughout the day.



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