Vision. You need good vision to drive safely. Most of what you do behind the wheel is based on what you see. If you cannot see clearly, you cannot judge distances or spot trouble, so you won't be able to do something about it.
Hearing. Hearing is more important to driving than many people realize. Your hearing can warn you of danger – the sound of horns, a siren, or screeching tires.
Even people with good hearing cannot hear well if the radio, CD, or tape deck is blaring. While driving, don't wear a headset or earplugs in both ears. It is against the law.
Alertness. When you are tired, you are less alert. You may not see hazards as soon or react as quickly, so the chance of a crash is greater. If you are sleepy, the only safe cure is to get off the road and get some sleep.
Medications. It is important to remember that all medications are potentially dangerous. Even over-the-counter medicines that you take for colds and allergies can make you drowsy and affect your driving ability.
Health and emotions. Whether you are calm, nervous, or hot-tempered, your personality affects the way you drive. Don't let your emotions interfere with safe driving. Use all the good judgment, common sense, courtesy, and safe driving rules that you can.