PURPOSE: To enable driving an automobile on several roads having various limited speeds at each regulated speed by assembling a detector in an automatic speed controller of an engine.

CONSTITUTION: The signal from a speed detector 10 consisting of an A.C. generator 1 and rectifiers 4, 5 is put into a permanent magnet 9 to move a coiled frame 8 up and down. The motion of the frame is transmitted to a distributing valve 20 up and down through a solenoid clutch 15. The valve 20 regulates the negative pressures to be applied to the negative pressure chambers 31, 32 of a diaphragm control valve 30. A rod 38 connects the valve 30 to a shaft 42 which functions in acceleration to close a throttle valve 51. An electric system 60 consisting of a clutch lever 68, a brake lever 69 and a momentary pushbutton switch 63 is connected to the solenoid clutch 15 and may stop the motion of the distributing valve 20 if it is of no use.