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The drivers of motor cars are obliged to restrict their speeds under some limit before the crossings over the major roads, railways and cross walks. Generally, the traffic signs or road markings are arranged before these crossings, but sometimes these indications are not followed by accident or design. The rugged roads are proposed to announce the crossings in advance and to force the lowering of the speeds. Several types of the rugged roads were provided and the vibrations of the motor cars and the road beds were measured under the various running speeds. When many button-­typed clots were setted on the surface of the pavement in short intervals (less than 50cm), the effect of the vibrations on the driver decreased as the speed of the motor car increased. Thus the button-typed road is effective to notice or warn that the motor car is approaching a crossing, but has no compulsive action to restrict its speed. When the up and down steps were laid on the pavement, the impacts applied to the bodies of the trucks were too severe, even they ran with the lower speed. The waves with the wave lengths of 4 through 8 meters were laid on the pavement. The acceleration of the vibrations in the body of the truck increased vigorously far before the resonant speed. So it is recommended to lay waves with wave length of about 10m.

The authors studied on the slacks in the turnout. The gage in the turnout must be extended due to the switch angle and the lead curve, but the extension of the gage, or the slack is restricted under the amount which is less than the theoretically calculated value to avoid the abrupt change of the gage and to secure the smooth running of the vehicles. Consequently the intense lateral forces are applied to the rails in the turnout under the wheels of the vehicles having large rigid wheel bases. The authors measured the bending stresses in rails of turnouts with prescribed slack and the larger one, and they concluded that the prescribed slack in the turnout should be enlarged to reduce the lateral pressure applied to the rails under the wheels of the large vehicles.

The lateral strength of the railroad track was measured. A test track with 50 kg rails, tie plates and wooden sleepers were laid on the crushed stone ballast. Vertical load up to 10 tons was applied on the track and sometimes vibrating force of the magnitude 565 kg was added to it. Then the lateral force up to 3.5 ton was applied to the rail head repeatedly and the lateral displacements of the rails and sleepers were measured. It was found that the sleepers creeped in the ballast as the lateral pressure increased and that some part of the lateral displacements of the sleepers remained after the lateral pressure was removed. The remained part of the lateral displace­ment was accumulated as the number of the repetition increased. When the vertical load on the track was not so large and the vibrating force was applied, the accumu­lation of the lateral displacements increased rapidly. It is supposed that the line of the railroads is disarranged in the similar way.

In a previous paper one of the authors analysed the lateral displacement of the railway track and the bending stresses in the rails under the lateral forces applied to the rail heads by a locomotive in motion, using the differential equation of the eighth order. The rails were assumed to be supported laterally by sleepers continuously along their whole lengths, as if they had been fastened on longitudinal sleepers. In the present paper the authors solved the same problem by using finite difference equations, assuming that the rails were supported laterally by sleepers laid uniform distances apart, and that the forces and the moments acting between the rails and the sleepers were proportional to their relative displacements and the angles of tilting of the rails respectively. Some numerical examples are shown and compared with the results given in the previous paper. The torsional rigidity of the rail enters into the above-cited calculations but, it had never been measured, the authors estimated it by torsional tests of the rail and by using the analogy between torsion of a rail and deformation of a thin film stretched over a hole in a flat plate.