Chapter 7 · Lesson 15 of 38
Rain, fog, wind and flash floods
5 min read · Safe Vehicle Operation
Explanation
Rain. Wet roads are most slick right after it starts to rain; your tires ride on a thin layer of oil, dirt and water. Hydroplaning increases with speed: if the tires touch only that layer, there is no friction to brake, speed up or turn. So: don’t drive on bald or badly worn tires, slow down in heavy rain, standing water or slush (and when water is deeper than your tread), pump your brakes after puddles to dry them, and use your headlights.
Fog. Drive slowly. Use low beams — high beams make it worse — and flashing emergency signals. If visibility drops to near zero, carefully pull off the road as far as possible and stop.
High winds strongly affect high-profile vehicles such as vans and SUVs.
Flash flooding causes more deaths than any other roadway weather event. Be extra alert at night and on unfamiliar roads. Never drive around barricades or past Road Closed signs, and don’t drive where water covers the road — its depth isn’t obvious and it may hide washouts. If your car stalls in flood water, abandon it as soon as possible.
Example
After a storm, water covers a dip in the road ahead. You can’t tell how deep it is, so you turn around and take another route instead of trying to drive through.
Common mistake
Using high beams in fog to “see farther.” The manual says not to use high beams in fog; low beams better light the road and objects ahead.
What the manual says
Hydroplaning increases with speed and at any point your tires may be in contact only with the oil, dirt, and water. If this happens, there is no friction to brake, speed up, or turn
Drive cautiously and at reduced speeds. Do not use high headlight beams. Low headlight beams better illuminate the road and objects ahead.
Flash flooding causes more deaths than any other roadway weather event each year.
Sources
- Manual p. 43
“Wet roadway surfaces can be dangerously slick, especially immediately following a rainfall.”
- Manual p. 43
“your vehicle is actually traveling on a thin layer of oil, dirt, and water which can lead to hydroplaning.”
- Manual p. 44
“Hydroplaning increases with speed and at any point your tires may be in contact only with the oil, dirt, and water. If this happens, there is no friction to brake, speed up, or turn”
- Manual p. 44
“Do not drive on bald or badly worn tires. Slow down when there is heavy rain, standing water, or slush on the road. After driving through water puddles, test your brakes by pumping them. Doing so will help to dry them.”
- Manual p. 44
“If the water is deeper than your tire treads, slow down. Use your headlights to be seen by other drivers.”
- Manual p. 44
“Drive cautiously and at reduced speeds. Do not use high headlight beams. Low headlight beams better illuminate the road and objects ahead.”
- Manual p. 44
“If fog closes in completely, and visibility is reduced to near zero, carefully pull off the road as far as possible and stop.”
- Manual p. 44
“Headlights and flashing emergency signals should be used while driving in fog.”
- Manual p. 44
“Strong winds have a significant effect on high-profile vehicles (e.g., vans and sport utility vehicles).”
- Manual p. 44
“Flash flooding causes more deaths than any other roadway weather event each year.”
- Manual p. 44
“Do not drive around traffic barricades or past road closed signs”
- Manual p. 44
“Do not drive where water is over the road, because the depth of the water is not always obvious, and the water may hide washouts”
- Manual p. 44
“If your car stalls in a flooded area, abandon it as soon as possible, because flood waters can rise rapidly and sweep a car and its occupants away”
Check your understanding
Question 1 of 3