**Personal mobility vehicles**, such as electric scooters and electric unicycles, have certain circulation restrictions. They cannot circulate on **roads outside urban areas**, which means their use is limited to **urban roads**.

- On **urban roads**, it is mandatory for drivers of these vehicles to wear a **safety helmet**. This is because, like other two or three-wheeled vehicles, they are more fragile and their drivers are at a higher risk of injury in the event of an accident.

- Additionally, these vehicles cannot circulate on **sidewalks, pedestrian areas, tunnels, crossings, highways, and expressways**. This reinforces the idea that their use is restricted to urban areas where wearing a helmet is mandatory.

Therefore, the correct answer is that wearing a helmet is mandatory on urban roads for drivers of personal mobility vehicles, as they cannot circulate on roads outside urban areas.