The adhesive properties between the train wheel and rail interface constrain railway traction power and braking effectiveness, affecting locomotive/rolling stock/track dynamic behavior and the lifespan of wheel-rail materials, which are closely related to safe train operation. Under low-speed conditions, the adhesive coefficient between the wheel and rail typically ranges from 0.2 to 0.4.

In actual operating conditions, it is observed that the adhesive coefficient of high-speed trains sharply decreases. For example, at a speed of 200 km/h, the minimum available adhesive coefficient for the French TGV is 0.09, with a test adhesive coefficient of 0.047.

Factors such as high-speed rolling, surface roughness of the contact surface, and the presence of third-party media such as water, which can reduce the adhesion between the wheel and rail, while adhesives can enhance adhesion. The mechanical properties of adhesives on the wheel-rail contact surface and their usage affect the mechanical behavior of wheel-rail rolling and the degree of damage to wheel-rail materials. 

Currently, there is no literature providing theoretical and numerical analysis on this aspect, and it is only based on empirical and experimental results that are applied to the study of engineering wheel-rail adhesion issues.

Another aspect of researching the improvement of traction and braking forces of high-speed locomotives is to consider the strength that the wheel-rail contact surface material can withstand. Because the most important factor causing fatigue damage to the wheel-rail contact surface is the tangential force (or friction force) between the wheel and rail.

 Blindly enhancing the adhesive effect between the wheel and rail can damage the wheel-rail contact surface, and in severe cases, lead to serious derailment accidents. Therefore, when improving the adhesion between the wheel and rail, it is necessary to consider a balanced development with the strength of the wheel-rail material.