1. Stopping Distance and Force of Impact
NV Driver Education Curriculum
Unit 5: Natural Laws and Car Control in Adverse Conditions
Presentation 4 of 6
TOPICS:
Thinking & Braking Time
Math & Physics of Braking
Force of Impact

2. The Law of Physics
No matter how good of a driver you are, the law of physics doesn’t change.
If you double your speed
from 30mph to 60 mph
Your braking distance is four times as long
Chart image from:
Retrieved 10/12/10
At 35 mph you need the length of a semi-truck and trailer to stop
At 70 mph you’ll need the length of a football field
On wet/icy pavement braking distance can be as much as ten times further

3. Rear End Crashes
Rear end crashes are the most common type of crash in the U.S. Leave a gap to avoid being a the cause of a rear end crash.
Silver Cars image from:
SUV image from:
3Sec image from:
Retrieved: 10/12/10

4. Distance travelled in yards
Thinking & Acting
Stopping a vehicle takes:
Thinking Distance: time for a driver to react to a situation
(increased by higher speed, tiredness, alcohol/drugs, distractions)
2. Braking Distance: time for vehicle to come to a complete stop
(increased by higher speed, poor road conditions, car equipment and weight)
Distance travelled in yards
Road image from:
Graph image from:
Retrieved 10/12/10
Speed of a car in miles per hour

5. Total Stopping Distance
Total stopping distance is based on good brakes and tires on dry, level concrete pavement.
Thinking Distance
Perception Time
Reaction Time
Braking Distance
Skid image from:
Chart image from:
Retrieved: 10/13/10

6. A vehicle continues to travel during thinking time.
Perception time is the length of time needed to identify a hazard, predict conflict, and decide to brake.
*three-quarters of a second
Reaction time is the length of time needed to apply the brake. *three-quarters of a second
A vehicle continues to travel during thinking time.

7. Braking Time
Braking time is the distance a vehicle travels from the point where the brakes are fully applied to when it comes to a stop.
Large skid image from:
Small skid image from:
Retrieved: 10/13/10

8. Mathematics of Stopping
A vehicle traveling at 60 mph travels 88 feet per second
Perception time = 1.1 x speed (1.1 x 60)
Reaction time = 1.1 x speed (1.1 x 60)
Braking distance = speed2 x (602 x 0.039)
Thinking time = 132 feet in 1.5 seconds
Braking time = 140 feet in 3.1 seconds
TOTAL stopping distance = 272 feet in 4.6 seconds
Approximately the length of 18 cars!
Image from:
Retrieved 10/13/10

9. In bad weather, braking distance grows exponentially.
On wet pavement, the 60 mph example will increase from 4.6 to 6.1 seconds and 333 feet.
In snow total stopping time jumps to 10.6 seconds and 533 feet
Wet image from:
Snow image from:
Retrieved: 10/12/10

10. Chart for traveling at 20 mph
Stopping on Ice
Use
Chains
Chart for traveling at 20 mph
Chart from: Pearson drive Right Textbook, 11th edition
Retrieved 10/20/10

11. The Physics of Braking Physics plays into braking:
Heavier vehicles have more momentum, thus take much longer to stop.
Friction of the brake pads against the wheel, and friction of the road work to stop vehicle.
When velocity/speed doubles (x2), braking distance goes up four times (x4).
Image from:
Retrieved: 10/12/10

12. Speed limits are created to keep all roadway users safe
Why Speed Limits
Speed limits are created to keep all roadway users safe
Image from:
Retrieved 10/12/10

13. Forces of Impact
Force of impact is the force with which a moving object hits another object. Force = Mass (weight) x Velocity (speed) Another consideration is the duration of impact (length of time for the vehicle to come to a complete stop)
Image from:
Retrieved: 10/13/10

14. Speed A vehicle’s momentum is proportional to its speed and weight.
55 mph crash
Hit wall - Caught on fire
2 teens dead on scene 3 others critically injured
70 mph crash
Driver lost control
1 teen dead on scene
1 critically injured
100 mph crash
Ran off road Car broke into 3 pieces
Teen driver dies after extensive injuries
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Teal car image from:
Brown car image from:

15. Weight
The heavier the vehicle, the more damage it will cause in the collision.
Even though the two vehicles may have the same speed and the same final speed, the smaller vehicle will sustain more damage.
Bus image from:
Truck image from:
Retrieved: 10/13/10

16. How quickly a vehicle stops affects the force of impact.
Duration
How quickly a vehicle stops affects the force of impact.
If vehicle is stopped in a very short time, the greater the impact.
Crumple zones reduce force of impact
Hitting a solid object (a wall) will have a greater impact than a less dense object (bushes).
Silver/Red crash image from:
Red/brown images from:
Van image from:
Retrieved: 10/06/10

17. Cars have brakes, but you don’t!
Think About It
Final Thoughts
Cars have brakes, but you don’t!
If you and the car are going 50 mph, when an impact occurs; the car goes from 50 mph to 0 in less than a second. Without a seat belt your body, also going 50, keeps going until it hits the dash or windshield.
Crash image from:
Ad image from:
Retrieved: 10/01/10

18. Speed & Braking PSAs Click on web address to access video clips
TAC Victoria
“Slo-Mo” Speed & Braking Collison
(1:00)
THINK!
Slow-Motion Braking Collision
(0:30)
Spain DGT
Speed & Braking Rear End
(in Spanish)
(0:32)
Click on web address to access video clips
*Suggest full screen viewing
NOTE: On Check access
Always preview video before showing to students
Check content
Check availability
YouTube image from:
Retrieved: 01/21/10

19. Speeding & Crashes PSAs
TAC Victoria
Wipe Off 5 (Hit Pedestrian)
(1:01)
THINK!
5mph Over (Hit Pedestrian)
(0:30)
Transport Safety
The Faster You Go The Bigger the Mess
(Rear End & Pedestrian)
(1:01)
Click on web address to access video clips
*Suggest full screen viewing
NOTE: On Check access
Always preview video before showing to students
Check content
Check availability
YouTube image from:
Retrieved: 01/21/10

20. Test Your Knowledge
If a car ahead of you has stopped at a crosswalk, you should:
Stop and then proceed when safe
Change lanes, look carefully, and pass
Slow down, look both ways, and proceed
Drive to the right edge of the road and stop
Answer: A

21. Test Your Knowledge
When a red light flashes at a railroad crossing, you must:
Stop only if you see a train coming
Stop 10 feet behind the signal
Stop and then proceed when safe
Slow down before crossing
Answer: B

22. Test Your Knowledge
This sign is commonly found in the middle of the road and means what?
Yield sign ahead
School zone ahead
No pedestrian crossing
Yield to pedestrians in crosswalk
Answer: D