[填空题]Sleep laboratories around the world are finding that an alarming number of drivers on motorways may be falling (36) at the wheel. Although researchers have difficulty in knowing for certain (37) an accident has been caused by sleepiness, it appears that a driver who is on the road between 4 am and 6 am is about 10 times as (38) to have a sleep-related accident as someone who is driving in the middle of the morning or early in the evening. Some British police forces have become sufficiently (39) to launch campaigns to alert the public to the danger. Leicestershire police, (40) , consider sleepiness to be the cause of 20 percent of accidents on motorways and in the summer of 1990 ran a campaign with the slogan "Stay awake, Stay (41) ". Major motor manufacturers such as Ford and Renault are (42) ways of incorporating sleepiness detectors and alarms into their vehicles.
If an accident involves only one vehicl