§ 35 StVO (6)
Vehicles used for the construction, maintenance or cleaning of roads and facilities in the road area or for refuse collection and marked with white-red-white warning devices may drive and stop on all roads and parts of roads and on each side of the road in each direction at all times, insofar as their use requires this, but only for the cleaning of pavements if the permissible total mass is up to 2.8 tonnes. The same applies to vehicles used to clean pavements whose maximum permissible mass does not exceed 3.5 tonnes and whose internal tyre pressure does not exceed 3 bar. It must be ensured that no damage can occur to the pavements and the supply lines below. Persons who are deployed for this purpose or who have to supervise roads or facilities located in their vicinity must wear conspicuous high-visibility clothing when working outside pavements and barriers.
These special rights allow, for example, a road sweeper to drive against the direction of travel. It is also possible to park a sewer cleaning vehicle in a no-parking zone if this is necessary to carry out the work. The special rights also form the basis for almost all work carried out by road maintenance services, from cutting shrubs and repairing damaged areas to installing traffic signs, etc.
In order for the special rights to be utilised, the vehicle must be equipped with 
warning markings in accordance with DIN 30710 | .
However, the standard not only describes the film design, but also how the individual surfaces are attached.
Detailed information on the correct application of warning markings can be found in the article 
Vehicle warning markings in accordance with DIN 30710 .
No special rights may be claimed without warning markings. Even if the order does not require any "special features", the special rights may not be used, even if the vehicle is marked. Furthermore, the specifications of the management must be observed, especially on federal motorways. In many cases, private companies are not permitted to use service ramps or service bypasses, even with marked vehicles, unless special regulations exist.
The warning marking is therefore not to be regarded as a "free pass". It does not authorise parking in a no-parking zone (e.g. to pick up bread rolls) or driving - albeit slowly - through red traffic lights in the roadworks area.
§ 35 StVO (8)
The special rights may only be exercised with due regard to public safety and order.
Source: https://www.gesetze-im-internet.de/stvo_2013/__35.html (translated)
