Fog on a Two-Lane at 2 A.M.
At 2:10 a.m., a driver is 90 miles from the terminal in a 26,000-pound box truck on a two-lane state route. The posted speed is 45 mph, the pavement is wet, and patches of fog reduce visibility to 100–150 feet, then clear without warning. The driver has been driving for six hours and has had coffee but no real break. High beams are on. The driver sees the taillights of a slower log truck ahead and considers closing to a one-second gap to use it as a guide. A moose crossing sign is visible, and the driver has already passed two dead deer on the shoulder. The truck's low beams are working; fog lights are not installed. The driver wants to reach the terminal by 4:00 a.m. and is considering speeding up in the clear patches to make up time.
1. What lighting and speed choices should the driver make in these conditions, and why are high beams a problem?
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The driver should switch to low beams. High beams reflect off fog and water droplets and create a wall of glare that shortens effective visibility, while low beams put light down and to the right. Without fog lights, low beams are the correct choice; hazard flashers may be used only as permitted and should not replace headlights. Speed must be low enough to stop within the visible distance. At 45 mph on wet pavement, stopping distance is well over 200 feet, more than the 100–150 feet of visibility, so 45 mph is too fast. The driver should slow to a speed that allows a stop in the distance seen, perhaps 25–30 mph or less in dense patches, and be ready to slow further. Speeding up in clear patches is a bad trade because fog can close in faster than the driver can react.
2. Evaluate the plan to follow the log truck's taillights at a one-second gap.
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A one-second gap is far too close even in good conditions, and it is worse in fog. The log truck can stop suddenly for a deer or a curve, and the box truck's wet-road stopping distance is long. Following taillights also creates a fixation effect: the driver watches the lights rather than the road, and if the truck drifts or brakes, the driver may react late. A safe following distance in poor visibility is at least four seconds, and many drivers use more. If the driver cannot see a safe path beyond the truck, the truck is not a reliable guide. The driver should back off, use the truck only as a distant reference, and be prepared to stop if visibility drops.
3. Visibility suddenly falls to about 50 feet, and the driver feels drowsy. What are the options, and how should a stop be made?
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At 50 feet, the driver cannot safely continue at highway speed. The first choice is to find a safe place to pull completely off the roadway, such as a parking lot, weigh station, or wide shoulder with solid ground. The driver should slow gradually, signal early, put the right wheels onto the shoulder, and stop as far from the travel lane as possible. Then set the parking brake, turn on hazard flashers, and keep headlights on low. The driver should not stop in the travel lane or on a narrow shoulder where the truck blocks traffic. If drowsy, the driver should not “push through” to the terminal; fatigue impairs judgment like alcohol. The driver should notify dispatch, take a rest break, and resume only when alert and visibility improves. If no safe pull-off exists, the driver should reduce speed further and use a controlled stop at the first safe place.