PROBLEM TO BE SOLVED: To provide an air speed reduction structure of a moving body capable of reducing the speed of an air stream generated on a periphery of the moving body by a simple structure at low cost.
SOLUTION: When a vehicle travels in direction A, air relatively flows in direction B between a bottom surface 4 of a vehicle body and a track R from a leading side of the vehicle 1 toward a rear tail side. As a result, the air flowing in direction B is disturbed by a truck 2, when it is peeled off from a side surface 5 of the vehicle body at a recession part 6 of the bottom surface, train air of a ballast surface relatively becomes faster and the ballast R1 is raised, soared and sometimes scattered. Peeling off of air flowing along the side surface 5 of the vehicle body is suppressed by a side plate part 7a and turbulence and peeling off of the air flowing along the bottom surface 4 of the vehicle body are suppressed by an inclination part 7b. Therefore, turbulence of the flow on the periphery of the truck is suppressed by the side plate part 7a and the inclination part 7b and flowing of the air on the surface of the track R is made smooth. As a result, the air speed on the surface of the track R is reduced and soaring of the ballast R1 is suppressed.