Section 5-8

The dashboard of your car gives you a lot of
information about your car’s ability to go

It gives no information about your car’s ability
to stop

How long do you think it takes just to switch
from the gas pedal to the break pedal?

The average, alert driver takes approximately
¾ of a second to 1 ½ seconds to switch from
the gas pedal to the break pedal.

This time is called the reaction time.

How far does a car traveling 55 mph travel
during this reaction time?

How many feet are there in a mile?
 5,280 ft = 1 mile

How many feet does a car traveling 55 mph
travel in 1 hour?
 (5,280 ft) x (55 mph) = 290,400 ft

How many feet does a car traveling 55 mph
travel in 1 minute?
 (290,400 ft) ÷ (60 min.) = 4,840 ft

How many feet does a car traveling 55 mph
travel in 1 second?
 (4,840 ft) ÷ (60 seconds) = 80.67 ft

If your reaction time is 1 second, then in the
time it takes you to realize you have to break
your car will travel approximately 81 ft

1.
Finding the distance traveled during reaction time
Find the distance traveled in feet in one hour
1. Multiply mph by 5,280
2.
Find the distance traveled in feet in 1 second
1. Divide step 1 by 3,600
3.
Multiply step 2 by the reaction time

A car is traveling at a speed of 65 mph. The
driver of the car has a reaction time of 1.5
seconds. How far will the car travel during
the driver’s reaction time?
1)
Find the distance traveled in feet in 1 hour:
→ (65 mph) x (5,280 ft) = 343,200 ft

A car is traveling at a speed of 65 mph. The
driver of the car has a reaction time of 1.5
seconds. How far will the car travel during
the driver’s reaction time?
2) Find the distance traveled in feet in 1 second:
→ (343,200) ÷ (3,600 ) = 95.33 ft

3)
A car is traveling at a speed of 65 mph. The
driver of the car has a reaction time of 1.5
seconds. How far will the car travel during
the driver’s reaction time?
Find the distance traveled during the reaction
time:
→ (95.33) x (1.5 ) = 143 ft

A car is driving on a rural road at a speed of
40 mph. The driver has a reaction time of
0.75 seconds. Find the reaction distance.
1)
(40 mph) x (5,280) = 211,200 ft
2)
(211,200 ft) ÷ (3,600) = 58.66 ft
3)
(58.66) x (0.75) = 44 ft

Page 272,
 Numbers: 1-3, 7 & 8
Section 5-7

1)
Previously, we covered two main topics:
Reaction time
1) The time it takes you to realize you need to brake
2)
Reaction distance
1) The distance traveled during your reaction time

What major factor do neither the reaction time
or reaction distance account for?

Note, both of those statistics just cover how
long and how far the car travels before you
realize you have to brake

They do not take into account how long it
takes your car to break

The distance a car travels while braking to a
complete stop is called the braking distance

What is the difference between braking
distance and reaction distance?

Why can braking distance vary depending on
time of year, location, etc.?

The general formula we will use for braking
2
distance is:
s
B.D. 
20
where “s” represents the speed of the car

Find the braking distance of a car traveling
48 mph.
2
s
s  48
B.D. 
20
2,304
(48)2

B.D. 
 115.2
20
20
It will take this car approximately 115.2 ft to
come to a complete stop.

Find the braking distance of a car traveling
65 mph.
2
s
s  65
B.D. 
20
4,225
(65)2

B.D. 
 211.25
20
20
It will take this car approximately 211.25 ft to
come to a complete stop.
Section 5-7
So far, we have covered two major concepts:
1)
Reaction Time/Distance
1) The time or distance you travel before you realize you
need to brake
2) Average between 0.75 and 1.5 seconds
2)
Braking Distance
1) The distance your car travels from the time you start
braking and when your car comes to a complete stop

Today, we will cover the final piece to these
concepts

Total Stopping Distance
 The distance a car travels from the moment a driver
realizes the need to stop to the time that the car
comes to a complete stop

Total Stopping Distance
 The formula for this is just the sum of the reaction
distance and braking distance

s2
=s
20
Where s is equal to the speed of the car

You are driving 65 mph on the highway. What
is your total stopping distance?
2
s
Stopping Distance = s 
20
2
65
65 
+
= 65 + 211.25 = 276.25
20
You have a total stopping distance of 276.25 ft

You are driving at 55 mph on a highway. You
see an accident directly ahead of you about
200 feet away. Will you be able to stop in
time?
s2
Stopping Distance = s +
20
552
= 55 + 151.25 = 206.25
= 55 +
20
You will not be able to stop in time 