PURPOSE: To eliminate inconvenience and danger of continuously depressing a pedal by operating a solenoid valve of a brake oil passage by a switch to close the brake oil passage, and shutting off all circuits when an accelerator pedal is depressed, to release the braking operation.

CONSTITUTION: When a push button 1 is depressed, contacts 2 are connected and a connected state of the contacts 2 is held by the operation of a relay 3. At the same time, a solenoid valve λ mounted to a brake oil passage is operated to close a hydraulic circuit, and even when the brake pedal is released, pressurized oil is maintained under pressure. On the other hand, a solenoid valve 5 is operated by connecting the contacts 2 and an elastic conductive plate 9 is protruded under the underside of an accelerator pedal D. In a moment the accelerator pedal D is depressed, the elastic conductive plate 6 and a contact plate 7 are connected, a relay coil 8 is operated to displace a relay contact 9 to a position 9. At the same time that the flow of current is shut off, the relay coil 3 is stopped to operate, the contacts 2 and 4 are separated, and the solenoid valve λ is stopped to operate to release braking.