Growing rail traffic worldwide requests higher safety standards and lower maintenance costs at the same time. An essential aspect is a continuous, trustworthy monitoring of wheel-rail interaction forces. Wheels of rail vehicles are exposed to high wear and tear. This may result in geometric wheel defects. The function PHOENIXMDS WDD/WIM measures on a continuous basis every wheel of the fleet and checks for any deviating force levels during normal train operation. Besides detecting wheel defects, the function is used as a dynamic rail scale at the same time. Vehicle weight and load distribution are monitored during every passage and an unbalance or overload can be recognized in time. Assistance for optimal payload usage is available as well.