a) the maximum longitudinal force that can be applied to a rail, secured to a sleeper, bearer or element of ballastless track by a rail fastening assembly, without non-elastic displacement of the rail occurring, or the longitudinal stiffness at a specified longitudinal displacement of a specimen of embedded rail with an adhesive fastening system, and for any type of fastening;

b) the shear displacement and slip data required for track-bridge interaction calculations.