01 Fire Apparatus Stopping Distance Flashcards
***** The total stopping distance includes four phases:
- Perception Distance
- Reaction Distance
- Mechanical Lag Distance
- Braking Distance
Perception Distance
Distance it takes the driver to perceive a hazard
Reaction Distance
Distance it takes the driver to react to the hazard
Mechanical Lag Distance
Distance it takes the vehicle to respond to the driver’s input
Braking Distance
Distance it will take the vehicle to dissipate its energy and come to a stop
Factors that play into total stopping distance:
- Reaction time of driver
- Road conditions
- Vehicles braking efficiency
- How forcefully the brakes are applied
- Speed of the vehicle
The time it takes for a person to detect, identify, and react to a hazard is known as
Perception and reaction time
The average perception and reaction time is:
1.6 seconds
The process of moving a person’s eyes is known as __________ and can be as long as _________ on a clear day.
Saccade / 1/3 a second
It can take a driver as much as _____________ to move their head all the way in one direction and all the way back.
1.7 seconds
The amount of kinetic energy depends on the vehicle’s:
size and speed
What are the three ways that a fire apparatus will dissipate its kinetic energy and come to a stop?
- Applying the brakes
- Skidding the tires
- Crushing the vehicle (wrecking)
Drag Factor
Coefficient of friction of the road surface + braking efficiency of the vehicle + slope of the roadway
The coefficient of friction typically ranges from:
0.2 to 0.9
In a vehicle equipped with air brakes, it takes longer for the brake system to fully engage. This time delay is known as:
Mechanical Lag Time or Air Pressure Lag Time
The braking distance of the vehicle is calculated using an equation known as the
Skid to stop formula
Several factors that effect a vehicles skid distance:
- Speed
- Road conditions
- Braking efficiency
- Slope of the road
A fire apparatus has a lower braking efficiency than a passenger vehicle. This reduced braking efficiency is a result of…
- The rubber composition of the truck tires
- Mechanical lag time of the air brake system
What formula will calculate the braking distance of a vehicle based on the conditions that were present at the time of the skid?
Skid to stop formula;
Conditions: speed, drag factor
