§ 58 StVZO
(1) A speed sign shall indicate the maximum permitted speed of the vehicle concerned in kilometres per hour.
(2) The sign must be circular with a diameter of 200 mm and have a black border. The numbers must be printed on a white background in black, bold, narrow type in accordance with Appendix V page 4 in a font size of 120 mm.
(2a) Speed signs may be retroreflective. Retroreflective speed signs must comply with standard sheet DIN 74069, May 1989 edition, and bear the DIN test and monitoring symbol with the corresponding registration number on the front.
(3) The following must be marked with speed signs
- Multi-track motor vehicles with a maximum speed of no more than 60 km/h as determined by their design,
- trailers with a maximum design speed of less than 100 km/h,
- trailers with an own mean braking deceleration of less than 2.5 m/s2.
(4) Paragraph 3 shall not apply to
- the tracked vehicles referred to in § 36 paragraph 10 sentence 6, second half-sentence,
- agricultural or forestry tractors with a maximum speed of no more than 32 km/h as determined by their design,
- agricultural or forestry implements carried behind motor vehicles.
The provision of § 36 paragraph 1 sentence 2 remains unaffected.
(5) Speed signs must be affixed to both sides and the rear of the vehicle. On agricultural or forestry tractors and their trailers, a speed sign on the rear of the vehicle is sufficient; if it is temporarily obscured or removed due to the nature of the vehicle or its use, a speed sign must be fitted on the right-hand side of the vehicle.
Source: https://www.gesetze-im-internet.de/stvzo_2012/__58.html (transleted)
Attaching multiple speed signs to vehicles
At the rear of many lorries there are up to four signs which are similar to the speed signs according to § 58 StVZO, but with a red instead of a black border. In Germany, these signs have no significance as there is a standardised regulation. In some countries, these signs are mandatory and apply to different types of roads, such as country roads or motorways. They can also be used to indicate certain driving situations, such as the loading of hazardous goods or travelling with a trailer. These signs can also be found on buses and caravans.
The information applies to the country in which the vehicle is registered and may vary from country to country.
