Vehicle-mounted pavement flatness detection system

The utility model relates to a vehicle-mounted pavement flatness detection system which comprises a detection vehicle and detection devices, the detection devices are installed on the vehicle head and the vehicle tail of the detection vehicle, and each detection device comprises a laser ranging assembly and an acceleration measurement assembly; the laser ranging assembly comprises a first shell; the acceleration measurement assembly comprises a second shell; air pressure rods are installed at the two ends of the first shell, one ends of the air pressure rods are fixedly connected with the first shell, the other ends of the air pressure rods are fixedly connected with the second shell, and the air pressure rods are coupled with distance detection circuits used for controlling the air pressure rods to be powered on and powered off. And when the air pressure rod is out of power, the relative positions of the first shell and the second shell are far away from each other. When the detection vehicle detects a narro