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Difficulty: EasyStopping Distance Components

Place the four sequential events of stopping an air-brake-equipped commercial vehicle in chronological order, starting from the moment a hazard is first spotted until the vehicle reaches a complete stop.

  1. 1The driver sees the hazard and the brain recognizes that braking is required (Perception phase).
  2. 2The driver releases the throttle and physically steps on the service brake pedal (Reaction phase).
  3. 3Compressed air travels through the lines to build pressure and push the brake shoes against the drums (Brake lag phase).
  4. 4Friction between the brake linings and drums slows the vehicle until forward motion stops (Braking phase).

Answer

The correct chronological sequence is: (1) Hazard perception, (2) Driver physical reaction to apply the pedal, (3) Air brake system lag while air pressure builds, and (4) Mechanical braking bringing the vehicle to a full stop.
Total stopping distance in an air-brake-equipped commercial motor vehicle consists of four distinct sequential phases: first, seeing and identifying the danger (perception); second, physically moving the foot to depress the brake pedal (reaction); third, the pneumatic delay for compressed air to travel through the brake lines (brake lag); and fourth, mechanical friction slowing the vehicle to a halt (braking).

Step-by-Step Solution

1
Identify the initial event upon encountering a hazard.
The perception phase occurs first as the driver spots the obstacle and recognizes the need to brake.
A driver cannot initiate stopping actions until the hazard is perceived.
2
Determine the physical action following hazard recognition.
The reaction phase occurs second as the driver physically moves their foot to press the brake pedal.
Physical muscular response takes time immediately following cognitive perception.
3
Identify the pneumatic system delay before friction begins.
The brake lag phase occurs third as compressed air rushes through the valves and lines.
Air takes roughly one-half second to build sufficient pressure to force shoes against the drums.
4
Identify the final phase that brings the vehicle to rest.
The braking phase occurs fourth as mechanical friction slows the wheels to a complete stop.
Actual deceleration friction continues from shoe engagement until the vehicle speed reaches zero.

Key Concept

The chronological four-component sequence of stopping an air brake commercial vehicle: Perception Distance + Reaction Distance + Brake Lag Distance + Braking Distance = Total Stopping Distance.
Estimated Time:45s
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Stopping Distance Components

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