**Special vehicles** are subject to certain **mass and dimension limitations** according to DGT regulations. This means that, although they are vehicles with particular characteristics, they must comply with some restrictions regarding their weight and size.

- **Maximum allowed weight:** All vehicles, including special ones, have a weight limit that they must not exceed. This limit includes the weight of passengers, luggage, and any other load. Exceeding this weight can damage vehicle components such as tires and braking and acceleration systems.

- **Maximum dimensions:** Special vehicles that exceed the measurements and weights established by the regulations have priority in certain situations, such as when passing through narrow areas. However, this does not mean they are exempt from complying with dimension regulations.

Therefore, special vehicles must respect certain weight and dimension limitations, which confirms that the correct answer is that they are indeed subject to some limitations.