PURPOSE: To permit the smooth speed change operation and improve workability by softening the shock on speed change by detecting the speed change operation and automatically reducing the number of engine revolution for a prescribed time after the detection point, particularly in a construction car.

CONSTITUTION: If a speed change lever 9 is operated when an engine is operated, setting a fuel control lever 1 at a high-idle position III, one among limit switches 11W13 is turned ON, and a relay 16 is operated through an OR circuit 14 and a one-shot circuit 15, and an electric power source 17 is connected to an electromagnetic actuator 8 through a selecting switch 18. Therefore, a rod 8a is extended by a prescribed amount in the A direction, and one edge 7a of an elliptical hole on a yoke 7 is engaged with a pin 5a, and a governor lever 5 is pushed back, and the number of engine revolution is reduced by a fuel injection pump 6. At this time, the movement of the governor lever 5 is absorbed by a cylinder 4 having a loose spring 4a, and the lever 1 is set inoperative.