The taillights of other vehicles are useful to motorists
- to estimate the distance of the vehicle.
- to judge the speed of the vehicle.
- to see the bumps or rough pavement. ✓
- to avoid blind spots of the vehicle.
Answer: C. to see the bumps or rough pavement.
The taillights of other vehicles help you see bumps or rough pavement ahead.
Why this is the answer
The handbook, in its night-riding advice, says to use the lights of the vehicle in front to get a better view of the road. It also says to watch that vehicle's tail lights: when they move up and down, that movement can warn you that the pavement is uneven. So the useful information is about the road surface, not about the other vehicle's distance, speed or blind spots.
Why the other answers are wrong
- A. to estimate the distance of the vehicle. — The handbook says distance judgment is weaker at night and tells you to leave extra space; it does not present tail lights as a way to estimate distance.
- B. to judge the speed of the vehicle. — Nothing in the passages says tail lights help you judge the speed of the vehicle ahead.
- D. to avoid blind spots of the vehicle. — Blind spots are not linked to tail lights in the passages, which describe tail lights as a way to read the road surface.
Remember it
Treat the tail lights ahead as a road-surface pointer: if they bob, expect a bump.