# me and you

Topics: Length, Automobile, Distance, Speed, Miles per hour, Vehicle / Pages: 5 (386 words) / Published: Sep 19th, 2014
Stopping Distance Formula e& Se eact!
R

PERCEPTION/REACTION DISTANCE + BRAKING DISTANCE = STOPPING DISTANCE
All drivers take a fraction of a second to perceive a hazard, and a fraction of a second to react before putting on the brakes. This time translates into perception and reaction distance—the distance your vehicle will travel in the time it takes you to perceive the hazard and to move your foot from the accelerator to the brake pedal. To figure your perception and reaction distance in feet, take the first digit of your speed, add it to the total speed and double it.

Speed

+

20 mph

First Digit = Perception/Reaction Distance

+

2

=

22 feet

x

2

=

44 feet

In other words, at 20 miles per hour, your vehicle will travel 44 feet in the time it takes you to see a hazard and move your foot from the accelerator to the brake pedal.
The faster you’re going, the further your vehicle will travel before you can hit the brakes.

Speed

+

55 mph
65 mph

First Digit = Perception/Reaction Distance

+
+

5
6

=
=

60 feet
71 feet

x x 2
2

=
=

120 feet
142 feet

Braking distance is also determined by speed. Here are braking distances for some speeds for a passenger car with well-maintained brakes on flat pavement in dry weather:

At…

Braking distance is…

20 mph
55 mph
65 mph

18 to 22 feet
192 to 224 feet
267 to 316 feet

Now we can calculate the stopping distance for these speeds:

At…

20 mph
55 mph
65 mph

Perception/
Reaction Distance

+

Braking
Distance

44 feet
120 feet
142 feet

+
+
+

18 to 22 feet
=
192 to 224 feet =
267 to 316 feet =

=

Stopping
Distance

62 to 66 feet
312 to 344 feet
404 to 458 feet

It’s easy to see that stopping distance is very much greater at high speeds than at low speeds. The faster you are going, the greater the distance you must allow between you and the car in front of you for safety. Wet conditions