1. Withstand the wheel weight and wear.
2. The wheel weight is dispersed to the sleeper under the rail.
3. Under constant pressure.
Regardless of the weight of the rail, the proportion of sectional quality should be roughly: head 42%, waist 21%, bottom 37%, and the height of the rail should be equal to the width of the bottom. When the rail head is worn up to 0.64 centimeters, the rail must be accessible immediately.