Accidents that are a result of driver fatigue might occur:

1. On narrow and winding roads only, and not in straight, wide and comfortable road sections.
2. On roads with long and steep descents only.
3. Correct answer: When the driver’s level of alertness decreases.
4. On roads with long and steep uphill sections only.

WhyA fatigue accident can happen on any road as soon as the driver's alertness drops. A straight, wide highway is even more dangerous in this respect.