Highway pavement will be particularly treacherous and most slippery:
- If it has been raining several hours.
- If it has just begun to rain. ✓
- If it has been raining for one to two hours.
Answer: B. If it has just begun to rain.
Pavement is most slippery just as it begins to rain.
Why this is the answer
The California handbook says the road can become very slippery when rain starts. It tells drivers to slow down at the first sign of rain, drizzle, or snow. It adds that this is especially true after a dry, hot stretch, because oil and dust have not yet been rinsed off the pavement. That fresh mixture is what makes the surface treacherous early in a storm, so the moment rain begins is the risky time.
Why the other answers are wrong
- A. If it has been raining several hours. — After rain has fallen for several hours, the handbook's point about oil and dust not yet being washed away no longer fits as well, so this is not the most slippery time it describes.
- C. If it has been raining for one to two hours. — A one- to two-hour rainfall is past the first sign of rain that the handbook warns about, when oil and dust are still fresh on the pavement.
Remember it
Think of the first raindrops as lifting oil and dust into a slick film, so ease off the gas right away.
Official handbook: California Driver Handbook (DL 600), Section 8: Safe Driving, p. 61