The **monotony of the road** is an external factor that facilitates fatigue while driving. This is because a monotonous road, without significant changes in the landscape or driving conditions, can lead to a lack of stimuli for the driver. This lack of stimuli can cause **psychological fatigue**, which manifests as a decrease in concentration and an increase in mental tiredness.

Fatigue is a significant risk in driving, as it affects the ability to concentrate and can lead to symptoms such as difficulty concentrating, heaviness in the eyes, and slower reactions to traffic situations. These symptoms are dangerous because they increase the likelihood of accidents.

Therefore, it is crucial to recognize that road monotony can be a trigger for fatigue and to take measures to mitigate its effects, such as taking regular breaks during the journey to rest and stay alert.