In order to decrease the lateral force generated in the railway vehicles in the curving sections, a simple steering system for the bolsterless bogie was developed. It is a simple steering bogie system that does not adopt complex bogie structure, and considered to be equipped with the function which prevents reverse steering movement. The most important feature of the developed system is that the system controls the steering force by the relative mechanical movement between the bogie and the car body that pass curving sections. That is, it is not based on the electrical control; the authors have designated this system as a "mechanical pneumatic steering system". This system is composed of pneumatic actuators that are built into mono-links, a mechanical sensing device of the bogie angle made by the relative movement between the bogie and the car body, and a pneumatic valve that works according to the sensing device. The sensing device for mechanical detection of the bogie angle is composed of two universal joints and a connecting rod that is expandable and contractile, but not revolvable. This device is able to transfer only the relative yawing angle between the car body and the bogie, and the other movement can be canceled by the motion of joints and the connecting rod. The mechanical pneumatic steering system with such features has been applied to a test bogie, and fundamental running tests were carried out in the test line in Railway Technical Research Institute. As a result, it is found that the average lateral force in a circular curve section with a radius of 160(m) is decreased by about 80% compared with the case where the steering control is not applied. In addition, we confirmed the basic safety of the reverse steering mode, which causes the controller failing.