For a traditional bicycle, in order to ride comfortably, the center of gravity must be behind and the legs must be placed on both sides of the front wheel: this will inevitably affect the steering of the front wheel. In order to solve this problem, either put your legs above the front wheel like lying on the car or increase the wheelbase of the front and rear wheels, then the bicycle will be too long and lose its flexibility. On the other hand, ordinary bicycles are designed for short-distance riding, and the riding time is generally not long, so riding by yourself is not a design consideration. But if it is a multi-person bicycle for leisure and sightseeing in the scenic spot, the backrest is very useful.