4.2 Horn, Headlights, Night Driving & Drowsy Driving

Your horn, lights and signals are how you communicate with other road users, and they matter most at night and in bad weather. This section covers the manual's rules for each, plus night driving and drowsiness.

Using the Horn

Never honk at a blind pedestrian (Section 10.1) or at an animal (Section 10.5).

When Headlights Are Required

You must use headlights and taillights:

1. From one-half hour after sunset until one-half hour before sunrise.
2. When you cannot clearly see people or vehicles 500 feet ahead because of poor light or weather.
3. Whenever you use your windshield wipers. Daytime running lights are not sufficient, because they often leave the taillights dark.

The manual also tells you to turn them on in rain, snow or fog, any time you have trouble seeing other vehicles, to alert another driver to turn on their headlights, and while driving through a tunnel.

Emergency Flashers

Use your emergency lights when your vehicle breaks down so others can see it. Move as far off the road as you can and stay out of the travel lanes. Never change a flat tire in a traffic lane; wait for help. Flashers can also warn drivers behind you of a crash or hazard ahead.

Advanced Driver Assistance Systems (ADAS)

Many vehicles now have systems such as lane-keeping, automatic emergency braking and adaptive cruise control. They help only when used correctly: read the owner's manual to learn what yours can and cannot do. You are still the most important safety feature in the car.

Night Driving

Night driving is more dangerous than daytime driving, because people, vehicles and obstacles are harder to see.

• Do not drive when you are tired or drowsy.
• Drive more slowly, especially in unfamiliar areas. Keep a speed that lets you stop within the distance you can see.
• Leave more space, especially near trucks and heavy equipment.
• Set the inside rearview mirror to "night" to cut glare from behind, and keep inside lights off.
• Do not look straight at oncoming headlights. Look toward the lower right side of your lane.
• Keep windows and headlights clean.
• If another driver flashes headlights at you, your lights may be off or your high beams may be on.

High Beams and Low Beams

Use high beams only in dark areas where you cannot see the road surface ahead. You must switch to low beams:

• Within 500 feet of an oncoming vehicle
• Within 200 feet of a vehicle you are following

If an oncoming driver keeps their high beams on, flick your lights once as a reminder. If they still do not dim, stay to the right and do not turn on your own high beams. Also dim your headlights at night when a bicyclist is coming toward you.

Overdriving Your Headlights

Low beams reach about 100 feet, but the manual's sample stopping distance at 30 mph is already about 104 feet, and at 60 mph it is about 292 feet (Section 4.1). On a dark road with low beams you can easily be driving faster than you can stop for something you suddenly see. Slow down or use high beams when legal.

Night-Driving Scenarios

1. An oncoming car keeps its high beams on: flick your lights once, then keep right and look toward the lower right side of your lane. Never answer with your own high beams.
2. You catch up to another car on a dark road: switch to low beams once you are within 200 feet of it.
3. Your headlights seem dim and the road is unfamiliar: slow down so you can stop within the distance you can see, and clean the lenses at your next stop.

Drowsy Driving

Drowsy driving can be deadly: 633 people died in drowsy-driving crashes in 2020, according to NHTSA. These crashes most often:

• Happen between midnight and 6 a.m., or in the late afternoon
• Involve a single driver with no passengers running off the road at high speed
• Occur on rural roads and highways

The only real protection is enough sleep. Coffee or a nap in a safe place helps only for a short time. Avoid driving between midnight and 6 a.m. when you can. Warning signs include drifting across lane lines and hitting rumble strips. Alcohol increases drowsiness, and many prescription and over-the-counter medicines carry drowsiness warnings, so check the label.

On long trips the manual recommends stopping to stretch every two hours or every 100 miles, and leaving the highway if you feel "highway hypnosis" setting in (Section 8.2).