They can be turned off by sending the vehicle home or by using the leftmost button.
Here are a few example vehicles with their respective matrix and a few examples of the functions.
City cleaning and some vehicles of the fire department for example the Lüdenscheider 14-TLF3000-01
Arrows to the left/right and cross
Arrows to the left/right + accident indication
Full blockage display
Armored personnel carriers/city cleaning:
Traffic guidance displays