Driving while sleepy
June 2006

Estimates of the proportion of car crashes attributable to sleepiness range from 3% to 33%, but little is known about the extent to which drivers are able to assess that they are sleepy while driving.

People continue to drive even when they know they are sleepy, suggests a large study published in the British Medical Journal today. This has important implications for public safety, say the researchers.

Researchers in France examined the association between self reported driving while sleepy and the risk of serious road traffic accidents (RTAs) in 13,299 middle aged drivers.

They collected data on sleepiness and other driving behaviours in 2001, and serious RTAs in 2001-3. Socioeconomic status was recorded, and a range of other factors that could affect the results were taken into account.

In answer to the question "in the past 12 months, have you ever driven while sleepy?" 63% of participants responded never, 36% a few times in the year, 0.8% about once a month, 0.3% about once a week, and 0.2% more than once a week.

There was a strong association between self assessed driving while sleepy and the risk of serious road traffic accidents over the next three years. This risk increased with reported frequency of driving while sleepy.

For example, participants who reported driving while sleepy "a few times in the year" were 1.5 times more likely to have been involved in a serious RTA compared with those who reported not driving while sleepy over the same period. And those who reported doing so "once a month or more often" were nearly three times more likely to have been involved in a serious RTA.

Further analysis did not change this association and follow-up questionnaires in 2004 also found a similar trend.

Messages on prevention should therefore focus on convincing sleepy drivers to stop driving and sleep before resuming their journey, they conclude.

Another study published today in the same journal, indicates that injury rates on England's roads remain high, despite government claims that they have fallen substantially. The number of serious injuries on England's roads is much higher than Government figures suggest, say the authors of this study.

Government targets for England look to reduce by 40% overall the number of serious injuries and deaths on the nation's roads by 2010, (compared with a starting point - baseline - of the 1994-8 average figures). The target for those aged 15 or under is higher, at 50% reduction.

But when researchers compared police statistics (which the Government uses for its figures), and hospital statistics between 1996 and 2004, they found large discrepancies.

Police figures showed that by 2004, numbers of those killed or seriously injured had dropped by almost a third (from 86 per 100,000 population, to 59 per 100,000). However, the police statistics showed a much smaller decline in the number of people killed than the number seriously injured.

Police statistics showed a 32% drop in serious but non-fatal injuries. However, the researchers found that hospital figures for non-fatal road injuries showed that rates had hardly changed between 1996 and 2004.

The authors suggest the discrepancies are probably down to an increase in under-reporting of injuries in the police statistics and that, if there has been a decline in injuries, it is probably only in those considered by the police to have been minor.

More investigation is needed, say the authors, since the findings cast doubt on whether there has been much progress on the Government's target to date - and on its likelihood of being met by 2010.

In practical and policy terms, much more needs to be done to ensure that there are real and substantial reductions in serious injuries not only on England's roads but as well in many other countries of the world.