The **generic maximum speed** is the speed limit that each type of vehicle must adhere to on different types of roads. For **motorcycles**, this limit is specific and cannot be exceeded under any circumstances on conventional roads.

- **Motorcycles**: They are not allowed to exceed the established maximum speed on conventional roads. This means that, unlike other vehicles such as passenger cars, motorcycles cannot increase their speed to overtake.

- **Exceptions**: Although some vehicles, like passenger cars, may have certain exceptions to exceed the maximum speed in specific situations, motorcycles do not have this flexibility.

Therefore, the correct answer is that the driver of a motorcycle cannot, under any circumstances, exceed the generic maximum speed on a conventional road.