What are the visual specifications for the mandatory warning panels (Warntafeln) used on wide agricultural implements?

1. They must be plain white boards with a black border
2. They must be solid orange rectangles without stripes
3. They must be red-and-white striped, but need not be retroreflective
4. They must be retroreflective, with alternating red and white stripes set at 45 degrees, facing outwards and downwards