Which of the following factors may affect a bus driver's ability to observe the road?

Fatigue is one of the most serious factors endangering road safety, as it significantly impairs the driver's psychophysical abilities. It causes reduced concentration, slower reactions, and a deterioration in visual acuity, which directly hinders proper and thorough observation of the road and its surroundings. In the case of a driver of a large vehicle, such as a bus, the effects of fatigue can be particularly dangerous.