Braking energy can be built up in many ways. Wanted is the most environmentally friendly solution, free from wear with as little as possible expenditure and weight. In any case, the retarder is better than the brake. It reduces its wear considerably, the more mountainous the merrier.
Here is a particularly good solution to the problem retarder: permanent magnets. They are arranged inside fixed in such a way that one is attached in north-south direction (red) and the two neighboring in south-north direction.
So that these permanent magnets do not continuously develop their braking force, now comes to it an intermediate ring twistable a few degrees. Its (blue) iron pieces are in normal driving so arranged between the permanent magnets, that the magnetic flux lines only run through it and not the actual wheel.
You could call it a kind of short circuit of the magnetic flux lines which is then abrogated, when the compressed air control in such a way rotates the intermediate wheel that iron cores and permanent magnets are lying upon each other. Now the magnetic power developed to the brake.
Here a long-known principle is applied. For now it seems to be usable only for medium-duty trucks and obviously not infinitely variable. But otherwise it seems to be enormously easier and lighter than a normal retarder system.
It will be interesting when this system is integrated into a hybrid platform. 06/12