Although I found a way to request additional information from Here-Api as described here, I am interested in how the speed data is particularly defined by. For instance, if "SP" is defined as Speed (based on UNITS) capped by speed limit, I would like to read up on what "capped by speed limit" means.
I found that this answer represents a model I am interested in. Particularly, I am interested in the difference between SU, SP, and FF.
Since the additional information provided in HERE API's XML request seems to be limited, I look for answers or links to more detailed explanations of the data mentioned above.