To urge a driver to subsequent self-discipline and prevent the breakage of a groove cover, by providing a transverse groove with load sensor, detecting the load of a vehicle passing on the groove cover, and informing an overloaded vehicle by displaying it.

This weight detecting system 20 is constituted of a transverse groove 10 with load sensors, a display board 12, and a control box 11. The transverse groove 10 with load sensors is provided with a U-groove and a grating 2a. Four load sensors are fitted at positions corresponding to four corners of the grating 2a. Each load sensor is mainly constituted of a weight coil spring and a limit switch. When a spring cover covered on the coil spring is sunk by a fixed quantity or above by a load, it is detected by the limit switch and transferred to the control box 11. When a microcomputer in the control box 11 judges the load to be an overload, a character of 'overload' is blinked on a display board to urge the driver of the vehicle to subsequent self-discipline.