The best answer is that heavy amphetamine use makes a driver less coordinated and at times more likely to be involved in an accident.
While amphetamines might give a sense of heightened alertness and confidence, they can be highly dangerous for drivers as they distort the driver's perception and can make him feel anxious, prone to panic and lose perception.
No illegal drugs can improve a person's driving, rather they make it worse. Therefore it is absolutely dangerous to use illegal drugs.
