REACTION STRETCH DESIGNATION
What is the reaction distance?
The reaction distance is the distance the car has time to travel from the time you detect a hazard until you press the brake pedal or swerve. The length of the reaction distance is affected by:
- Speed of the car
- Driver reaction time
The reaction distance increases proportionally with the speed of the car, which means that if you travel at 100 km/h, the reaction distance is twice as long as when you travel at 50 km/h. The reaction time varies slightly from person to person but is normally 0.5-2 seconds. People between 45-54 years old have the best reaction time.
EASY AND APPROXIMATE METHOD
Calculate reaction distance
There are two different methods for calculating the reaction distance:
- Lighter and approximate method: Reaction distance = Speed (remove last digit) * reaction time * 3
If you drive at 50 km/h, the calculation of the reaction distance is:
5*1*3 = 15 meters
If you drive at 100 km/h, the reaction distance is 10*1*3 = 30 meters.
As we see in the example, the reaction distance is doubled when the speed is doubled. As mentioned earlier, it increases proportionally with the speed of the car!
MORE DIFFICULT AND ACCURATE METHOD
Computation reaction distance
- More difficult and precise method: Reaction distance(s)= (v*r)/3.6
v = speed km/h
r = reaction time (seconds)
If you drive at 50 km/h, the calculation of the reaction distance is as follows:
(50*1)/3.6 = 13.9 m.
As you can see, it's pretty easy to figure out the reaction distance. If the question appears on the theory test, it is not expected that you will be able to figure it out in your head using the exact method. You can use the approximate method to get an approximate result. The important thing is that you understand that the reaction time and your speed affect the reaction distance!