FATAL FLAW IN DRIVER SLEEPINESS RESEARCH
19 October 2004 - Safe Speed

On the day that the DfT releases new research proving that driver sleepiness is a huge road safety issue, Safe Speed warns that vital factors are still not even being considered.

Nevertheless, Safe Speed strongly supports the DfT''s initiative to raise public awareness of the important consequences of driver sleepiness.

The factor that is being ignored is the crucial relationship between speed and driver attention. When forced to drive too slowly by traffic or by regulations we risk getting bored and not paying full attention. Poor attention strongly contributes to the risk of falling asleep at the wheel.

There is plenty of science to explain the relationship between ''work rate'' and attention levels. Too much work and we get stressed and perform badly. Too little work and we get bored and perform badly. In the middle of the range is optimal work rate and optimal attention levels.

It should be obvious that driving slowly leads to a low work rate and boredom while driving too quickly leads to very high work rates and stress. Yet, according to Professor Jim Horne, no research has been carried out into the subject.

Paul Smith, founder of the Safe Speed road safety campaign explains: ''It''s very simple. We need our drivers to operate in the optimal range as much as possible. We need them to be fully engaged in the task of driving - neither stressed nor bored. The vast majority of drivers will find a safe and appropriate balance for themselves. But - and this is important - the correct balance varies from individual to individual.''

Paul continues: ''Forcing motorists to drive at standard speeds, frequently below their optimal range, will simply exacerbate problems with driver inattention and driver sleepiness. As usual, the Government has no research to offer into this particular side effect of ''speed kills'' road safety policy.''

Heavy Goods Vehicles:

The DfT tells us that 1 in 3 sleep related road accidents are caused by heavy goods vehicle drivers. Yet HGVs only make up about 1 vehicle in 8 in the motorway traffic. With tachographs, working hours restrictions and better training why are HGV drivers nearly three times more likely to fall asleep at the wheel?

We need to consider the following factors:

* Good vehicles travel at a lower speed, so the same mileage takes longer. The exposure to the risk of falling asleep is increased by about 20% to 30%.

* Heavy goods vehicle drivers choose to travel at quiet times - perhaps the early hours of the morning - more than other drivers.

But these factors are nowhere near sufficient to explain the increased risk of falling asleep that HGV drivers face, especially given their higher levels of training and their working hours restrictions.

Safe Speed believes that the critical difference is the psychological ''fall out'' of driving with the compulsory 56mph speed limiters fitted to all heavy goods vehicles since 1996. The speed limiter has three direct effects on driver attention levels:

1) Since most motorway conditions are suitable for a constant 56mph, HGV drivers do not need to control their speed. They leave it to the limiter. This reduces their work rate and reduces their interest in the task of driving.

2) 56mph is quite a modest speed for UK motorways in typical conditions, even for a heavy goods vehicle. We know that it is a modest speed because needing to slow below 56mph for safety is infrequent. Driving below an optimal speed requires rather less than 100% attention from the driver. Performance at the task suffers. Basically drivers are bored. The most extreme form of this tendency to low attention is actually falling asleep.

3) A constant speed provides a constant drone from engine, transmission and tyres. The constant drone itself is soporific.

Despite 8 years of HGV speed limiters, no research has been carried out into the road safety consequences yet plans to fit limiters to a wider range of vehicles are progressing.

Conclusions:

Safe Speed demands far better thinking behind our road safety policies. The constant neglect of side effects demonstrates a woeful lack of understanding of ''how road safety works'' at the highest political and academic levels.

www.safespeed.org.uk

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