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Difficulty: EasyStopping Distance Components

A commercial motor vehicle equipped with air brakes requires a total stopping distance of 290 ft290\text{ ft} to come to a complete halt from highway speed. The event breakdown includes a perception distance of 100 ft100\text{ ft}, a driver reaction distance of 45 ft45\text{ ft}, and an air brake lag distance of 30 ft30\text{ ft}. What is the vehicle's remaining braking distance, in feet?

Answer: 115 ft

Answer

115 ft
For commercial vehicles equipped with air brakes, total stopping distance is the sum of four distinct components: perception distance, reaction distance, brake lag distance, and effective braking distance. Subtracting the known pre-braking distances (100 ft+45 ft+30 ft=175 ft100\text{ ft} + 45\text{ ft} + 30\text{ ft} = 175\text{ ft}) from the total stopping distance of 290 ft290\text{ ft} yields an actual braking distance of 115 ft115\text{ ft}.

Step-by-Step Solution

1
Set up the commercial vehicle air brake stopping distance formula
Total Stopping Distance = Perception Distance + Reaction Distance + Brake Lag Distance + Braking Distance
Air brake systems have four distinct sequential components that contribute to the overall stopping distance.
2
Sum the given perception, reaction, and brake lag distances
100 ft + 45 ft + 30 ft = 175 ft
This establishes the total distance traveled before the brake linings actually contact the drums/discs.
3
Subtract the non-braking distances from the total stopping distance
290 ft - 175 ft = 115 ft
Subtracting the pre-braking distance from the total stopping distance leaves only the mechanical braking distance.

Key Concept

Four components of total stopping distance in air brake systems
Estimated Time:45s
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Topics

Stopping Distance Components

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