The coefficient of friction provides an indication of the degree of floor slipperiness.
The B.C.R.A. method (English) measures a surface’s coefficient of dynamic friction (μ) and classifies:

μ <0,19 - dangerous slipperiness;
0,20< μ < 0,39 - excessive slipperiness;
0,40< μ < 0,74 - satisfactory friction;
μ >0,75 - exellent friction.

The DIN 51097 method for bathroom floors and wet feet (see swimming pools) applies the inclined plane method. The standard includes the angles of slippage. Angle classification: A >12°; B >18°; C >24°. 

DIN 51130 for the prevention of accidents and industrial safety, classification of flooring materials in terms of the critical angle of slippage. (Angle -> Group): (>6°-10°-> R9); (>10°-19°-> R10); (>19°-27°-> R11);(>27°-35°-> R12), (>35°-> R13).