| 摘要 |
PURPOSE: To grasp the condition of the road surface of a road network over a wide range in real time by a method wherein an ultrasonic wave is emitted toward the surface of the road to receive the reflected wave from the surface of the road and a reflection factor thereof is measured to determine an acoustic impedance proper to material from the reflection factor. CONSTITUTION: An ultrasonic wave 17 is emitted toward the surface 11 of a road downward vertically from a transmitter/receiver 13 and the reflected wave 18 thereof is received 13 to measure energy of the received wave 18. An arithmetic means 14 calculates a reflection factor of the reflected wave attributed to the road surface 11 from energy of the received wave 18 measured. The arithmetic means 14 further calculates an acoustic impedance of the road surface 11 from the reflection factor determined. At this point, temperature correction of sound velocity is performed based on an outside air temperature inputted from a thermometer 16 through a wire 20. The acoustic impedance obtained from the road surface 11 is inputted to a judging means 15 and compared with a reference acoustic impedance in a memory to be classified as dry, wet, snow, sherbet, frozen, in terms of condition to be shown on a display device of a central managing room or the like. |
