Testing requirements for mechanical couplings to 94/20/EC are:
Fatigue test: Each fifth wheel is subjected to loads both in a vertical and horizontal direction for 2 million cycles calculated to simulate the maximum loads that the fifth wheel would see in operation. This is a rigorous test that will not accept any cracks in the test piece.
Steering wedge test: This applies a load to simulate the sideways forces generated when using a steering wedge (this is used sometimes to control rear axles steering of trailers). Again neither deformation nor cracking is allowed.