Lifestyle and exercise

Time to change the clocks?

Moving clocks forward would cut road deaths in Scotland,” reported The Guardian . It said a new study claims that moving the clocks forward by an hour all year round would cut road deaths, improve health, and benefit industry and tourism in Scotland.

The news story is based on an article in the British Medical Journal , and a report by the Policy Studies Institute (PSI). Both are opinion pieces by Dr Meyer Hillman, who is in favour of the UK time zone being permanently moved forward by an hour in winter, and by another hour in summer. He argues that such a move would align most people’s waking hours with daylight, providing numerous health and economical benefits.

The report focuses on the benefits for Scotland in particular, as those in opposition of such a move have often argued that the loss of daylight in the morning there would offset any benefit of the extra light gained in the afternoons and evenings.

The report makes a strong case. However, these are the author’s views and interpretations of the evidence, and there may be other unconsidered evidence. Also, as the author acknowledges, many of the figures presented are estimates only. This review alone will probably not solve the debate. Further research and consideration of public opinion would probably need to take place before any changes were made.

Where did the stories come from?

The news stories are based on an article in the British Medical Journal , and the publication of a report by the Policy Studies Institute (PSI). Both were written by Dr Meyer Hillman, who works for the PSI. The report states that the views and interpretations of the evidence are entirely those of Dr Hillman, and should be considered in this context. Similarly, the BMJ article is a personal opinion piece.

The PSI carries out research relevant to social, economic, industrial and environmental policy in the UK. It is reportedly one of the UK’s leading research institutes aimed at promoting economic wellbeing and improving quality of life. Dr Hillman received funding from the Crescent Trust. No methods are provided in the PSI report or the BMJ piece.

What is the issue?

The report discusses the debate over how the UK should change its clocks to conserve daylight hours during the summer and winter months. Currently, the UK conforms to Greenwich Mean Time (GMT) during the winter, and British Summer Time (BST) in the summer when the clocks move forward by one hour. The report argues for this to be changed so that the clocks are permanently moved forward by an hour in winter, and then by another hour in summer.

This proposed arrangement is called ‘Single Double Summertime’ (SDST). The author says the time shift is supported by road safety organisations, the tourism and leisure industry, trade bodies, sporting, cultural and recreational facilities, youth groups, and those supporting pensioners and people in rural communities.

There are two sides to the debate, however. Some are concerned that the most northerly parts of the UK would lose a considerable amount of daylight in the morning, offsetting any benefit from the extra light gained in the afternoons and evenings. The debate has been hampered by the lack of an evidence-based assessment of the costs and benefits for Scotland. The report therefore presents many of the expected benefits of advancing daylight hours for this region.

What would be the potential benefits of the suggested change?

The report says that a change to SDST would have the following benefits:

  • Alignment of waking hours with daylight: the report says that a shift to SDST would be better matched to when the majority of people get up and go to bed. Adults working normal 9-to-5 hours would gain 300 additional hours of daylight every year, and would only be affected by the later sunrise on about 60 weekdays in winter. It says that children in Scotland would gain 200 extra daylight hours a year, with about half of these falling on school days.
  • Road Safety: the report says that surveys show that road crashes are more likely to occur during the evening peak-time hours, due to less visibility and reduced driver attentiveness. If the evening peak-time was in daylight, the number of accidents would be expected to go down. A 1998 study by the Transport Research Laboratory on the impact of the clock change on road safety estimated that SDST would lead to an overall reduction of 0.7% deaths and serious injuries on Scotland's roads, with a 0.2% reduction in casualties of all severities. Applying this to 2009 road casualty figures for Scotland, the author suggests that with SDST there would be 20 fewer deaths or serious injuries per year, with 30 fewer casualties of all severities. Figures from the Department for Transport suggest that reductions in road casualties by this amount would save about £8 million per year.
  • Tourism: the report estimates that a change to SDST would boost tourism revenues by £3.5 billion a year and generate around 80,000 jobs in the UK. In Scotland, it is estimated that this would boost earnings by £300 million and provide 7,000 more jobs. Currently, tourism is responsible for about 11% of the Scottish economy.
  • Sport and leisure: surveys find that the majority of people prefer to do sports and other outdoor leisure activities during daylight hours. Therefore, it is suspected that an extra hour of daylight in the evenings will result in more people taking advantage of sports and recreation facilities.
  • Health: health and wellbeing is expected to increase as a result of more people taking part in sport and recreation. There may possibly be a reduction in levels of Seasonal Affective Disorder (SAD), and people may get more vitamin D through daylight exposure.
  • Electricity consumption: advancing the clocks could lower electricity demand on every evening of the year due to a reduced need for artificial light. Demand in the morning would only rise in the winter months. The report estimates that Scottish domestic electricity bills would be reduced by 1.5%, saving Scottish bill-payers around £15 million annually.
  • Carbon emissions: due to the fall in demand for artificial lighting in the evenings, less greenhouse gas emissions from power stations would be expected. Carbon dioxide emissions from power stations across the UK would potentially drop by about 450,000 tonnes.
  • Better security: many crimes, e.g. muggings and vehicle thefts, occur after nightfall. Fear of crime is higher in the dark, so lighter evenings could lower society's sense of vulnerability, especially parents, who may otherwise put restrictions on their children.
  • Trade and industry: SDST would align the UK more closely with the working hours of other countries, thus potentially improving trade and economic relations.
  • Farming: this is an area where a change to SDST might be expected to have a negative impact due to a loss of morning daylight. However, the report counters this by saying that all dairy cows are already milked in artificially lit automated parlours from October through to April. Also, new farming techniques are said to have reduced the need for work in the very early morning. The report says that the National Farmers Union in Scotland have a ‘neutral’ stance on the issue of advancing daylight hours.

The opinion piece in the BMJ focuses on the potential benefits of advancing daylight hours in terms of increased recreation, and relates this to the UK’s growing obesity epidemic. The author highlights the 300 extra daylight hours a year that adults would have for activity, and the 200 extra daylight hours for children.

What are the interpretations of the author?

The author concludes that the evidence gathered in the report indicates that advancing the clocks “would bring the Scottish people at least as great benefits as those predicted for the rest of the UK”. Scottish poll findings indicate an even divide in support for and against the change. This he says, ‘adds up to an exceptionally strong case for reform’.


This is a wide-ranging report in which the author has gathered together survey findings and national figures to give an estimate of the benefits from a change to what is termed ‘Single Double Summertime’ (SDST).

The report provides various pieces of evidence to support the move, and describes the many potential benefits. It is important to note that much of the predicted benefits are estimates, and it is difficult to know whether all possible factors have been taken into account. With regard to the reduction in road deaths in Scotland in particular, these figures are based on estimates from a 1998 study by the Transport Research Laboratory (TRL). As the author of the current report says, the TRL report acknowledged a fair degree of uncertainty in their estimates and “there are strong grounds for suggesting that they are conservative”. Therefore the reduction in deaths and casualties should be considered with due caution.

As with all narrative reviews, and as this report acknowledges, the views and interpretations of the evidence are entirely those of the author. The report should be considered in this context, and there may be other evidence that has not been considered, which could support the opposing view. If the change were to be made, it is difficult to know in advance what effect the darker mornings would have when people are heading to work and school. Currently the vast majority of British school children go to school and leave school during daylight hours all year round. Single Double Summertime would mean most children would be travelling to school in darkness during the winter months.

NHS Attribution