Following Distance on a Foggy Freeway
You are driving north on a freeway at 65 mph at 5:30 a.m. Dense fog reduces visibility to about 100 feet. You are in the right lane, and a truck is 80 feet ahead of you. The road is wet, and your tires are worn. You see taillights ahead but cannot tell whether they are in your lane or the next lane. Your exit is 2 miles ahead, and you are running 10 minutes late for work. Your passenger suggests speeding up to pass the truck before the exit.
1. What following distance should you maintain, and how does the fog change the basic rule?
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The basic rule is at least three seconds in good conditions; in fog, rain, or other poor visibility, increase it substantially. At 65 mph you travel about 95 feet per second, so 80 feet is less than one second of following distance - far too close. In fog with 100 feet of visibility, you should slow down and leave enough space to stop within the distance you can see, which at highway speed may mean well over 300 feet. Because you cannot see far, reduce speed so that your stopping distance fits inside the visible distance. Passing the truck would put you closer to unseen hazards, so do not speed up.
2. What should you do about your exit and about the worn tires?
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Do not rush to make the exit. If you miss it, continue to the next exit rather than making a sudden lane change in fog. Worn tires reduce traction on wet pavement and lengthen stopping distance, so slow down further and avoid hard braking or sharp steering. Check your tire tread when it is safe to stop. The 10-minute delay is not worth the risk; arriving late is better than crashing.
3. What lights should you use, and what should you do if the fog becomes so thick you cannot see the road ahead?
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Use low-beam headlights, not high beams, because high beams reflect off fog and reduce visibility. If fog becomes so thick you cannot see, slow down and, if necessary, pull off the road completely, turn on hazard lights, and stay in the vehicle with seat belts fastened until conditions improve. Do not stop in a travel lane. Do not use hazard lights while driving unless your vehicle is a hazard or you are following the rules for a disabled vehicle.