53.8. Where does the air go after releasing the brake pedal?
UAКуди дівається повітря після відпускання педалі гальма?
Question without image
This exam question concerns the safe operation of vehicles and understanding how the brakes work while driving. It is important for a driver not only to know the traffic rules, but also to be aware of what happens in the braking system when the pedal is pressed and released, because the speed of brake release and the serviceability of the actuators affect controllability and stopping distance, and therefore road safety.
In essence, it tests a topic that, in study materials, is covered alongside the Traffic Rules of Ukraine during preparation for the theoretical exam: the structure and technical maintenance of vehicles, in particular the pneumatic brake drive. There is no direct provision in the sections of the Traffic Rules of Ukraine about the direction of air release, but the technical principle is studied: when the pedal is released, the pressure in the brake chambers must be quickly relieved, so the air exits through the brake valve and exhaust (release) valves to the outside, which is often heard as a characteristic hissing sound.
The correct answer is the option where the air is vented into the atmosphere, because this is how the pneumatic system unloads the brake chambers and allows the springs to return the mechanisms to their original position. The idea that the air "returns to the system" is incorrect for the working cycle of pneumatic brakes: it is not returned to the reservoirs, the pressure is released through the exhaust. And the statement about supplying it to the engine intake manifold does not relate to the brake drive at all; it may be associated with other vehicle systems, but does not explain the operation of pneumatic brakes in the context of traffic rules and exam preparation.
Traffic Rules of Ukraine: direct provision is absent
The current Traffic Rules of Ukraine do not contain clauses that regulate or describe the principle of operation of the pneumatic brake system (in particular, where the compressed air is released after the brake pedal is released). Such a question does not pertain to the provisions of the Traffic Rules, but rather to the educational section "Structure and technical maintenance of vehicles" (pneumatic brake drive), where it is studied that after releasing the pedal, the pressure from the brake chambers is discharged outside through exhaust (release) valves.
Therefore, the correct answer is "It is vented into the atmosphere," given that the Traffic Rules do not specify any other procedure for the operation of the pneumatic brake drive, and according to the technical principle of pneumatic brakes, the air is released (vented) outside after the pedal is released to disengage the brakes.
In a pneumatic brake system, pressing the brake pedal is a command to brake: compressed air from the reservoirs is supplied under pressure through the brake valve to the brake chambers. There, the air pressure creates a force that presses the brake mechanisms and slows down the movement of the vehicle.
When the driver releases the pedal, the command changes to stop braking. In order for the brake mechanisms to return to their original position, the pressure in the brake chambers must be quickly released. For this purpose, the brake valve and exhaust (release) valves open an outlet to the outside, and the air from the chambers is released not back into the reservoirs, but outside.
This is why after releasing the pedal we often hear a characteristic hissing sound near the wheels or under the frame: this is not a "leak," but the normal venting of air through the valves, which ensures rapid brake release.
Therefore, the correct answer is "It is vented into the atmosphere," because when the pedal is released, the pressure in the brake chambers is released through the exhaust valves to the outside so that the brakes are disengaged.