From which width onwards must truck tractors be equipped with these warning plates?

Your answer is correct. According to German traffic regulations, truck tractors must have these warning plates when their width exceeds 2.75 meters.

The warning plates serve to alert other road users to the vehicle's increased width, which can pose a danger on roads, especially in narrow lanes or when overtaking. This rule helps improve safety by ensuring that oversized vehicles are clearly visible and recognizable from a distance.

In the image, the distance marked "X" represents the overall width of the tractor. If this width is greater than 2.75 meters, the warning plates on the sides are mandatory to warn other drivers.

Remember this rule to correctly identify when oversized vehicles require special marking, enhancing road safety for all.