The **reflective vest** is a mandatory safety element for truck drivers. Although the provided excerpts do not specifically mention the reflective vest, it is important to understand that its use is a general safety measure to improve the driver's visibility in emergency situations or when the vehicle is stopped on the road.

- **Visibility and safety**: The reflective vest helps make the driver visible to other road users, especially in low-light conditions or in emergency situations. This is crucial to prevent accidents and ensure the safety of the driver and other road users.

- **General safety obligations**: Although the texts focus on other safety aspects, such as the use of lights and mirrors, the reflective vest is part of the safety measures that drivers must follow to comply with traffic regulations and protect themselves and others.

Therefore, it is mandatory for a truck driver to carry a reflective vest in their vehicle to ensure their safety and that of others on the road.