35.24. What is the danger of prolonged braking with the clutch (gear) disengaged on a steep descent?
UAЧим небезпечне тривале гальмування з вимкненим зчепленням (передачею) на крутому спуску?
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This is an exam question from the Traffic Rules of Ukraine about safety when driving on steep and long descents, where a vehicle rapidly gains speed under the force of gravity. The topic is important for the theoretical exam because it is directly related to the driver's ability to maintain control over the vehicle and correctly choose a safe speed in difficult conditions, as required by the traffic regulations.
The question tests the section of the Traffic Rules regarding speed and driver actions in hazardous situations (specifically the requirements of points 12.1 and 12.3), as well as practical driving basics: why it is not allowed to coast for a long time with the clutch disengaged or in neutral on a descent. In this mode, engine braking is lost, and the driver is forced to use the service brakes for an extended period, which operate through friction and inevitably heat up.
The correct answer explains the main risk: it is the overheating of the braking mechanisms that leads to a decrease in braking efficiency, an increase in stopping distance, and the danger of partial or complete brake failure (in particular, due to possible boiling of the brake fluid). Other answers do not reflect the key threat: tire wear is not the main consequence of such a descent, and “increased wear of brake components” is possible, but it is secondary compared to the critical loss of efficiency due to overheating. In practice, the correct tactic to meet the requirements of the Traffic Rules of Ukraine is to reduce speed in advance, engage the appropriate gear, and use the brakes with short presses for correction, not for constant “holding” of speed.
Clause 12.1
When choosing a safe driving speed within the established limits, the driver must take into account the road situation, the characteristics of the cargo being transported, and the condition of the vehicle in order to be able to constantly control its movement and drive it safely.
Application to the question: on a steep (long) descent, driving with the clutch/gear disengaged deprives the driver of engine braking and forces prolonged use of the service brakes, which worsens the ability to “constantly control the movement” due to reduced brake efficiency (overheating).
Clause 12.3
If a danger to traffic or an obstacle arises, which the driver can objectively detect, he must immediately take measures to reduce speed up to stopping the vehicle or safely bypassing the obstacle for other road users.
Application to the question: loss of brake efficiency due to their overheating on a descent without engine braking creates a danger, because in a critical situation the driver may not be able to “immediately” reduce speed up to a stop.
Clause 2.3 (subclause "a")
To ensure road safety, the driver is obliged: before departure, to check and ensure the technical serviceability and completeness of the vehicle, and the correct placement and securing of the cargo.
Application to the question: prolonged braking on a descent with the clutch/gear disengaged creates an operating mode in which the braking mechanisms overheat and actually lose efficiency (that is, the technical serviceability/operability of the brakes while driving may be lost).
Therefore, the correct answer is: "The braking mechanisms overheat and braking efficiency decreases," given that according to the definition of the Traffic Rules, the driver must choose a safe speed and drive in such a way as to constantly control the movement and be able to timely reduce speed up to a stop, and overheating of the brakes on a descent without engine braking reduces this possibility.
On a steep or long descent, the car tends to constantly accelerate under the force of gravity. To maintain a safe speed, the driver must either reduce speed using engine braking (driving in gear), or continuously "hold" the car with the service brakes.
When the driver disengages the gear or presses the clutch and coasts, the engine is effectively disconnected from the wheels. In this mode, the engine braking effect disappears, and the speed increases more rapidly on the descent. The driver is then forced to brake for a long time and often only with the brake pedal to avoid exceeding a safe speed.
The service brakes operate on the principle of friction. If you brake for a long time on a descent, the braking mechanisms heat up more and more. Due to overheating, braking efficiency decreases: the pedal may become "softer," the stopping distance increases, and the car slows down less effectively even with greater pressure on the pedal. In extreme cases, the brake fluid may boil, which can lead to a sharp decrease or loss of braking.
That is why it is safer on descents to reduce speed in advance and engage the appropriate gear, so that part of the deceleration is provided by the engine, and the brakes are used with short presses to adjust speed, rather than for constantly "holding" the car.
Therefore, the correct answer is "The braking mechanisms overheat and braking efficiency decreases," because when the gear (clutch) is disengaged on a descent, engine braking disappears and you have to brake for a long time with the service brakes, which overheats them and reduces their effectiveness.