In built-up areas you can find lamp posts that are marked with red and white reflective signs. Those signs are an official traffic sign in Germany (no. 394). They are used on lamp posts to indicate that streetlight does not stay on all night which can be a measure used by cities and municipalities in order to save energy.
The sign can be applied in the shape of a rigid sign (size 70 mm x 150 mm) or as a reflective band around the lamp post (width 70 mm) which is the more commonly seen version. The red area has a width of 50 mm and the white stripes on top and bottom measure 10 mm each. The lamp post ring has to be applied at a height between 1.50 m and 1.80 m.
In our shop you find the sign acc. to StVO as 
self-adhesive reflective tape | or rigid sign on aluminium composite | .
Legal foundation:
The obligation to mark lamp posts that do not stay on throughout the night results from the fact that parking vehicles need to be illuminated at night according to sec. 17 (4) StVO:
“Within built-up areas, it is sufficient either to illuminate only the side of the vehicle facing the carriageway by means of the vehicle’s parking lights or to mark it in any other permissible way; if the street lighting makes the vehicle clearly visible at a sufficient distance, lighting using the vehicle’s own light source can be dispensed with.”
When parking your vehicle, it is therefore important to pay attention whether the lamp post is marked with the reflective sign and, if necessary, to switch on the parking lights during the dark hours. Non-compliance may result in a fine.
The times when street light is switched off may be indicated in the red area of the sign.