The **maximum speed** allowed for a **bus** on a **motorway** is **100 km/h**. This is because traffic regulations establish specific speed limits for different types of vehicles and roads to ensure road safety.

- In the case of **buses**, the maximum speed on **motorways and dual carriageways** is **100 km/h**.

- These limits are set to ensure that all vehicles travel safely and comfortably, taking into account the type of road and its conditions.

- Although on motorways and dual carriageways it is possible to travel at speeds of up to 120 km/h, this limit applies to light vehicles, not to buses.

Therefore, the maximum speed of **100 km/h** for buses on motorways is a safety measure aimed at reducing the risk of accidents and their possible consequences.