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RAC Editorial

The effect of British Summer Time on Transport

26 Mar 2012 at 10:40

By Richard Aucock

With the turning forward of clocks signalling the arrival of spring, many motorists are buoyant at this time of year – the prospect of driving home in daylight after the daily commute in the darkest depths of winter bringing with it an optimism for the summer ahead.

And while the subconscious effects of a one-hour forward shift may have a positive effect on people, there are also positives for road transport that a move to British Summer Time brings with it.

The benefits: reduced accident rates

There is an extensive body of research evidence showing that clocks going forward reduces road traffic accident rates and, therefore, overall casualties.

A three-year trial of British Summer Time in the UK from 1968 to 1971 – as opposed to rolling the clocks back an hour to Greenwich Mean Time come the end of October – recorded an overall reduction in the number of people killed or seriously injured on the roads.

Individual trends concluded that an increase in road traffic incidents occurred in the mornings, due to longer hours of darkness, but that the reduction in deaths and serious injury sustained on the nation’s roads – thanks to the improved visibility longer daylight hours bring – far outweighed the small morning rise.

Although the first tests on the impact of turning the clocks forward on road traffic were conducted shortly after the 70mph motorway speed limit and drink-drive laws were introduced in 1965 and 1967 respectively, later analysis confirms that staying lighter for longer, thanks to the clocks going forward, means fewer accidents on the nation’s roads.

The Transport and Road Research Laboratory carried out further investigation into the original results back in 1989 – allowing for the drink-drive legislation – and came up with some quantifiable numbers that show how the one-hour switch can help save lives.

The outcome? If a year-round alteration to BST was made, 160 fewer people would have been killed, 650 fewer seriously injured and 2,060 fewer motorists and pedestrians would have sustained any form of injury altogether.

Divide those numbers in half due to the six months (roughly) of longer light we get in the UK when the clocks go forward, and it shows the positive effect the change can have on road transport.

Of course, back in the late ‘80s, the UK’s road death toll stood at 5,125 people per year, over two and a half times that of today’s annual rate of 2,000 lives lost. This is an improvement thanks to increasing advances in car safety, brought about by more stringent crash tests and regulations, but also improvements to the UK’s roads.

Even so, the argument that a one-hour advance ahead of GMT reduces accidents is still hard to ignore.

Campaigns such as carbon-cutting organisation 10:10’s Lighter Later movement – backed by road safety charity Brake and comprising a shift to the GMT+1/GMT+2 March/October time structure in the UK – certainly put forward some convincing arguments for the clocks going forward having a positive effect on drivers.

Under this scheme, clocks would shift forward by an hour throughout the year, so the extra hour of daylight would shift from the morning to the afternoon. An official Daylight Saving Bill, in favour of the shift, has already been discussed in the House of Commons back in January, but the debate ran out of time to be resolved. Due to continued support from more than 90 organisations, it is hoped this will again be discussed by MPs in May.

Support for the bill comes from the Royal Society for the Prevention of Accidents: it says that, during the working week, casualty rates on the roads peak at 8am and 5pm for adults, and 8am and 3.30pm for children. It’s easy to see why: the frequency of both peaks coincice with peak travelling times for work and school.

On top of this, road casualty rates increase as the darker nights and associated worsening weather conditions draw in. But according to data from 10:10, a complete winter step change to the one-hour advance UK drivers have to deal with every March – further advancing one hour to GMT+2 time every spring – can help curb needless and tragic road deaths even more.

That means between 80 and 100 lives and 200 serious injuries saved every year. That statistic alone is enough to prove the benefits for road transport in the clocks going forward.

But the plus points of the one-hour wind-on are not just centred around an improvement in accident and casualty rates, even if saving just one life makes the move warrantable.

Benefits to the environment and the economy as a result of the clocks going forward are felt, too.

Due to the longer daylight hours and associated reduction in need for electricity across the country, CO2 emissions are reduced by around 220,000 tonnes – that’s equivalent to the output of 25,000 vehicles, proving road transport is not the worst belcher of black smoke it sometimes unfairly gets labelled.

Thanks to the reduction in accident rates, the clocks going forward should save the NHS £70 million pounds in treating individuals involved in collisions, too.

It’s clear to see, then, that a simple switch in time – effectively shifting daylight hours one hour later – can provide some real, tangible benefits for road transport. But that doesn’t necessarily mean the outcome for drivers and pedestrians is all good.

The drawbacks: lack of alertness

Setting the clocks forward may seem like a fairly trivial part of the approach to the spring and summer months, but the possibilities for fun and leisure driving brought about through gaining that extra hour of daylight in the evenings is tempered by an hour’s more darkness in the mornings.

Although seemingly unimportant, this can have a serious effect upon road transport.

For motorists driving after the clocks go forward, “sleep time” is effectively reduced by one hour (presuming individuals go to bed at the same time as usual). In conjunction with darker conditions in the mornings, it can take some drivers up to a week to readjust.

According to Marks and Spencer Car Insurance, it takes 49 per cent of Brits to get used to the clocks going forward – not necessarily conducive to an alert commute to work or run to school.

With one hour less sleep all that is needed to disrupt certain peoples’ routines, behind-the-wheel concentration levels might not be as high and you might not have quite the edge to your reactions you might think.

Team this with poorer visibility as a result of the low light, and it’s not hard to see where the observed increase in accident rates in spring and summer mornings comes from.

That said, motorists have to cope with driving to work in the dark routinely in winter so are well aware of keeping lights and windows clear, and their cars in good mechanical and roadworthy order to help improve safety.

We’re willing to bet concentration levels are higher on average in the mornings after the clocks going forward than on the drive home following a full day at the office, though…

Other issues

It is possible that drivers coming home from work once the clocks have gone forward are not in as much of a rush to get back – trying to catch the daylight for social and leisure activities, for instance – as they might be in the light-limited winter months.

Naturally, if you’re in less of a rush, you’re less likely to speed – not only reducing the risk of speeding and having an accident on your own, but involving other road users and pedestrians as well.

On the flip side, some drivers could be in more of a rush if alarm clocks aren’t suitably adjusted the night before and on board vehicle clocks don’t get changed, meaning minds are elsewhere other than on the road and the task in hand.

Some high-end vehicles may change the time automatically, often updated through information sent through RDS or digital DAB radio signals to the car’s on-board computer.

But for some owners, the increasingly integrated electronics of modern vehicles mean it can be a trial and error method of fumbling through menus and sub-menus to reach the right location to re-set the time.


The main effect on road transport of the clocks going forward is positive. Improved driving conditions – better visibility being the main factor – leading to lower accident rates should be welcomed by all.

Keep vigilant in the first few days after the switch, and always make sure driving is the sole focus of your concentration, and the one-hour change should make motoring much more of a pleasure. It won’t make an hour’s less sleep any easier to bear, though…

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