Place. People often don't realize how close they are to falling asleep even when their eyelids are falling shut. If you can safely do so, look at yourself in a mirror. If you look sleepy, or you just feel sleepy, stop driving You are in a very dangerous condition. The only safe cure is to sleep. 2.12 – Driving in Fog Fog can occur at anytime. Fog on highways can be extremely dangerous. Fog is often unexpected, and visibility can deteriorate rapidly. You should watch for foggy conditions and be ready to reduce your speed. Do not assume that the fog will thin out after you enter it. The best advice for driving in fog is don’t. It is preferable that you pull off the road into a rest area or truck stop until visibility is better. If you must drive, be sure to consider the following Obey all fog-related warning signs. Slowdown before you enter fog. Use low-beam headlights and fog lights for best visibility even in daytime, and be alert for other drivers who may have forgotten to turn on their lights. Turn on your way flashers. This will give vehicles approaching you from behind a quicker opportunity to notice your vehicle. Watch for vehicles on the side of the roadway. Seeing taillights or headlights in front of you may not be a true indication of where the road is ahead of you. The vehicle may not be on the road at all. Use roadside highway reflectors as guides to determine how the road may curve ahead of you. Listen for traffic you cannot see. Avoid passing other vehicles. Don’t stop along the side of the road, unless absolutely necessary.