The reason for this requirement is for the safety of passengers.
If the speed of the handrail belt is slower than the speed of the steps, if the grasping position is not adjusted according to the situation after grasping the handrail, it will drive the human body to lean backwards and easily make passengers fall, especially elderly passengers.
If the handrail belt is a little faster, people's arms will automatically extend forward with the handrail, which will reduce the inclination of the body.
Of course, the ideal state is that the steps are synchronized with the handrails. However, after running for a period of time, due to the wear of various components, the handrail drive device will slightly slow down the running speed of the handrail belt.
Therefore, in the escalator design, in order to avoid the situation that the handrail belt is slower than the step after running for a period of time, the initial theoretical speed of the handrail belt is about 1% faster than the step speed.
In addition, the instructions for taking the stairs clearly require "grasping the handrail" instead of "leaning on the handrail". "Leaning on the handrail" is the wrong posture when riding a ladder. You lose the function of adjusting the speed difference with your arms, and it's easy to fall down.