Who is not required to use a seat belt, as a general rule?

Traffic regulations state that all drivers and passengers of cars traveling on urban or interurban roads are required to properly wear their seat belt. Despite this, there are some exceptions, such as the one that states that when taxi drivers are in service in urban traffic or urban areas of big cities, they are exempt from wearing their seat belt. On interurban roads, dual carriageways and motorways, it is always obligatory for them to wear their seat belt.