Changing the clocks

The way the clocks are set in the UK means for much of the year, most of us waste daylight in the early mornings while we're asleep, and then have to make our way home in the dark in the evening.

In the UK, clocks follow Greenwich Mean Time (GMT) from October to March, and British Summer Time (BST), which is GMT + 1, from March to October. This means Britain is out of step with most European countries, which follow Central European Time (CET), which is always one hour ahead of the UK. It also means that in winter, it gets dark as early as 3.30pm in some parts of the UK [1].

Why are darker evenings dangerous?

During the week, casualty rates peak between 5pm-6pm for adults, and 3.30pm-4.30pm for children. There is another peak in the morning, 8-9am, but the afternoon peak is higher for all ages [2]. These times coincide with the morning and evening rush hours and school runs, which are already dangerous due to the volume of traffic, and even more so in the winter months when the evening journeys are made in the dark.

Road casualty rates increase with the arrival of darker evenings and poor weather. For example, in 2013 there were more than twice as many pedestrian deaths in December as in June [3]. It has been observed that each year from when the clocks go back in October, the peak in evening road casualties shifts so it falls in the hour after sunset [4]. Research has also found that serious and fatal pedestrian collisions increase 10% in the four weeks after the clocks go back [5].

There are several reasons for the increase in casualties in the darker winter evenings. First, pedestrians and cyclists, road signs, and other road users are simply harder to spot. Drivers also tend to be more tired after a day’s work, so concentration levels are lower in the evenings than in the mornings [6]. Finally, both children and adults tend to make social or leisure trips in the evening [7] (such as visiting friends, or children taking part in after-school activities), so in winter have to make these journeys after dark.

Take action: Make the Brake Pledge to minimise the amount you drive, or not drive at all, and get about by walking, cycling or public transport as much as possible, for road safety, the environment and your health.

How should the clocks be changed?

Brake is calling for the UK to change to Single/Double British Summertime (SDST), adjusting the clocks to GMT+1 in the winter, and GMT+2 in the summer. This would result in darker mornings but an extra hour of evening daylight throughout the year.

It is estimated this would prevent 80 deaths and more than 200 serious injuries on UK roads every year. The initial, one-off cost of making and publicising the change is estimated at about £5 million, which would be more than offset by the benefits of the change, amounting to £138 million per year [8]. Analysis has projected a net benefit of £2.5 billion over 20 years, from reduced casualties [9].

As well as reducing casualties, SDST would deliver a range of other benefits, to the environment, health and tourism:

  • Environment: switching to SDST would reduce CO2 pollution by at least 447,000 tonnes each year, due to reduced electricity demand for artificial light in the evenings [10].
  • Health: Longer evenings would encourage more people to be active, using the extra daylight hours for outdoor leisure and sporting activity [11]. Daylight is also known to reduce depression and Seasonal Affective Disorder (SAD) [12].
  • Tourism: SDLT would allow an extended tourism season and longer summer opening hours of tourist facilities, boosting the UK tourism industry by £1bn every year [13].

Previous trials

From 1968 to 1971, the UK ran an experiment in which British Summer Time (GMT+1) was employed all year round. The clocks were put forward as usual in March 1968 and not put back until October 1971. 

Analysis of crash data [14] during this period showed that keeping BST during the winter months resulted in an 11% reduction in casualties in England and Wales during the hours affected by the time change. In Scotland, there was a 17% reduction in casualties. Although casualties in the morning increased slightly, the decrease in casualties in the evening more than outweighed this.

Overall, about 2,500 fewer people were killed or seriously injured during the first two winters of the experiment. The experiment coincided with the introduction of roadside breath tests and the 70mph speed limit, which may have also had an impact on the casualty reduction figures.

Despite the reduction in casualties, continuation of BST past the trial period was blocked by a vote in the House of Commons. The opposition was due to the small rise in early morning casualties (despite these being outweighed by the huge reduction in evening casualties), and concern over disruption to early-morning workers such as farmers and postal workers.

In 1989, researchers analysed casualty data from winter 1969/70, in the middle of the experimental period, and concluded that BST had resulted in 232 fewer deaths and serious injuries and 2,342 fewer overall casualties during that one winter, taking into account wider trends and other road safety factors like roadside breath testing. The study concluded that BST was effective in reducing casualties, particularly among children, pedestrians, and people in central England and southern Scotland [15].

Why not change to SDST?

In previous years, a move to SDST has been opposed on the grounds that it would disrupt industries that operate in the early hours of the morning, such as farming, milk delivery, and postal workers. However, there is increasing evidence that these objections are less relevant. For example, post deliveries now take place later in the day than when the 1968/71 experiment took place, and are usually staggered throughout the day [16]. Modern farming methods have reduced the impact on farmers, with many (including the National Farmers’ Union for Scotland [17], who previously opposed the change) now neutral or positive about a move to SDST.

There has also been opposition to the change from Scotland, due to a mistaken impression from misleading reports that the 1968/71 experiment increased casualties, and a perception that the change would only benefit England. This is untrue: the reduction in casualties during the 1968/71 experiment was greater in Scotland than in England and Wales. Due to its shorter daylight hours to begin with, Scotland would benefit disproportionately in safety, economic, health and all other measurable areas compared with England and Wales [18].


[1] Sunrise/set times for the United Kingdom, HM Nautical Almanac Office, 2014

[2] Single Double British Summertime Factsheet, RoSPA, 2013

[3] Reported road casualties Great Britain 2013, Department for Transport, 2014, table RAS30020

[4] Daylight hours, Road Safety Observatory, 2012

[5] Improving Road Safety for Pedestrians and Cyclists in Great Britain, National Audit Office, 2009

[6] Fatigue and Road Safety: A Critical Analysis of Recent Evidence, Department for Transport, 2011

[7] Single Double British Summertime Factsheet, RoSPA, 2013

[8] A Safer Way: Making Britain’s Roads the Safest in the World, Department for Transport consultation paper, 2009

[9] Policy briefing – single/double summertime, Parliamentary Advisory Council for Transport Safety, 2010

[10] Daylight saving, electricity demand and emissions: the British Case. In: The Future of Electricity Demand, Customers, Citizens and Loads, Cambridge University Press, 2011

[11] Daylight Saving Survey, YouGov, 2009

[12] Single Double British Summertime Factsheet, RoSPA, 2013

[13] The likely impact on tourist activity in the UK of the adoption of DST, Policy Studies Institute, 2008

[14] Review of British Standard Time, Home Office, 1970

[15] The potential effects on road casualties of Double British Summer Time, Transport Research Laboratory, 1989

[16] Why do I receive my mail at different times? Royal Mail, undated

[17] “We're not against moving clocks forward an hour, say Scottish farmers, The Guardian, 2010

[18] Single Double British Summertime Factsheet, RoSPA, 2013


Page last updated: September 2014

Tags: clock change light winter summer