Driving a two-wheeled vehicle, such as motorcycles and mopeds, is more dangerous mainly because **they are less visible to other drivers**. This is due to several reasons:

- **Reduced visibility**: Two-wheeled vehicles are smaller and, therefore, more difficult to see in traffic. This increases the risk that other drivers may not detect them in time, especially when changing lanes or at intersections.

- **Greater fragility**: In addition to being less visible, these vehicles are more fragile compared to other cars. This means that, in the event of an accident, the consequences can be more severe for the drivers and passengers of two-wheeled vehicles.

- **Additional precautions**: Drivers of other vehicles must take additional measures to avoid accidents with motorcycles and mopeds, such as maintaining an adequate safety distance and ensuring there are no two-wheeled vehicles before changing lanes.

In summary, the reduced visibility of two-wheeled vehicles in traffic is a key factor that contributes to their increased danger.