Daylight saving: improving productivity or a major health and safety concern?

Categories: Salford Business School

With this week marking the bi-annual event of switching the clocks, the relative merits and disadvantages of daylight saving time (DST) briefly enter public debate. As dinner table conversation, everyone has their own personal anecdote.

University of Salford Business School’s Dr Gordon Fletcher, School Lead for Research, grew up in a location where the arguments against daylight saving had won favour. Those arguments? That daylight saving fades the curtains and confuses the cows. Not a very strong evidence base to make decisions. Even worse, it was the sight of still-closed curtains on an early morning summer ride that become the original inspiration for one of the most vocal advocates for daylight saving in the 20th century, William Willett.

There are only three possible outcomes to any daylight saving debate. Maintain the cycle of switching between standard and daylight saving times, permanent standard time or permanent daylight saving time. But, there are a vast array of scientific arguments for and against each of these options. Here, Dr Fletcher explores them…

The economic argument: reducing energy consumption and improving productivity

The original purpose for introducing the bi-annual cycle of daylight saving is primarily an economic one. The case that is made is that moving clock time forward in spring reduces energy consumption and improves productivity. There is less need to turn on the lights in the workplace, factory or farm. This argument finally persuaded politicians in WWI to adopt DST in 1915. While this may seem like quite a recent introduction, it is worth remembering that standard time (or Greenwich Mean Time) was only formalised in 1880. And standard time had only became a necessity with the development of the rapid transit offered by cross-country trains and more importantly, train timetables.

The health and safety argument: battling between the sun, body and social clocks

More recent arguments have focused on the health and safety issues relating to bi-annual daylight saving time. Medical researchers put it best when they describe daylight saving as a battle between the sun clock, the body clock and the social clock. The sun clock is the observed natural clock which equates midday with the sun being at the highest point in the sky. The body clock relates to our own rhythms for sleep and relative exposure to light and dark. The social clock is the time that appears on our watches and other devices.

Social clocks and sun clocks align during standard time but only on the meridian that we set our time from - which is Greenwich in the UK. If you live west or east of this, meridian social clocks will not quite line up with the sun clock. The social clock of Belfast and Margate office workers for example are not the same, with around 30 minutes difference between sunrise in the two locations currently. Factor in the difference in daylight hours travelling between the north and south, and this influence on our body clock also helps to explain why being a domestic tourist within the UK can sometimes feel so disorientating. Factoring in consideration for differences in body clocks between ages, as well as those who are "night owls" or "early birds," and the battle of daylight saving appears very personal.

From a safety point of view, this is where the problems arise. Every time there is a change in the social clock to or from alignment with the sun clock, accidents happen. Shifting the daytime away from the evening causes road accidents as tired workers drive home in the dark, we have slower reactions due to fatigue and children struggle to adjust to bedtime. Losing an hours sleep in March also creates tired workers whose body clock is displaced, and this can lead to workplace errors and accidents that can aggregate to millions of pounds in lost productivity. This is not a problem experienced over a single day and has been shown to last many weeks. There is also some medical evidence for an increase in heart attacks with the spring change in clocks.

Permanent daylight saving time or standard time avoids these safety, health and productivity issues. But this can place some at a permanent disadvantage with the social clock constantly being out of sync with their own body clock. Perhaps following Billie Eilish and the trend for wearing two watches could be put to good purpose. It also inspires a rewriting of Segal's Law: a person with one clock knows what time it is. A person with many clocks is never sure.

Switching up the social clock

The debate is particularly important for the EU where the decision to abandon bi-annual changes in the social clock was voted for and agreed. However, the implementation is still to happen. The Central European Time Zone stretches from Spain to Poland and means that sunrise in Madrid and Warsaw currently varies by 99 minutes. A variation that also helps to explain why there are differences in timings for social activities across the continent.

The UK has also experimented with social clock options in the past. Between 1941 and 1945, during WWII, the UK enjoyed permanent double summer time with the clocks set two hours forward (a note for all historical filmmakers). Permanent daylight saving was also introduced between 1968 and 1971, but abandoned after a free vote in the House of Commons.

There are strong arguments for maintaining a single social clock throughout the year. The Royal Society for the Prevention of Accidents estimates that 2,500 less people were killed or seriously injured in the winter during the permanent daylight saving period, between 1968 and 1971. This was an 11.7% reduction; even though a number of additional injuries occurred in the mornings, the decrease in evening accidents far outweighed this.

But, the bi-annual resetting of the clocks has become part of the cycle of annual rituals that bring us shared opportunities for conversation that are not directly about the economy, politicians or global instability. Everyone has a daylight saving story to share and that is important too.

For all press office enquiries please email communications@salford.ac.uk.