The breeding of dogs who suffer from a short snout is prohibited by law, whether it is for purebred dogs or crosses. Until recently it was difficult to maintain this, because there were no clear criteria. Therefore, Utrecht University has proposed the traffic light model: with red light should not be bred with a dog; If it's orange, then there can be bred dog and all other features are good; the green light should be raised, unless other features are red.

Red, orange or green nasal length.
With the new criteria simply a yardstick to determine whether a muzzle is short for breeding if the nose length covers less than 1/3 of the skull length, the traffic light is red. That means with a skull 10 centimeters that the muzzle must be longer than 3.3 centimeters. Measure the snout half or more of the skull length, it is the traffic light to green and can be bred (if there is at least no other features are in red)