When do sleep-related road crashes occur?

• They occur on dull roads, usually early in the morning, at times when your body clock signals sleep, between 4 am and 6 am, especially the 'early start to beat the rush'.
• They involve speeding and driving too close.
• There is no evidence of braking before the accident.
• There are no personal medical defects.
• The driver could not see the impact point several seconds before the collision, so there is prolonged inattention.
• Nightworkers and truck drivers are especially at risk.

But, when questioned by the police, drivers deny falling asleep for fear of prosecution and loss of insurance cover. Many also suffer 'traumatic amnesia', and cannot recall the collision.