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

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: http://www.driveandstayalive.com/info%20section/stopping-distances.htm 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

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: http://www.car-accident-compensation.com.au/CAR-ACCIDENT-CAUSES-TYPES-FREE-ONLINE-CAR-ACCIDENT-COMPENSATION-ADVICE.html SUV image from: http://thecarinsuranceinsider.com/insurance-news/beware-these-accident-scams/ 3Sec image from: http://www.allpageranks.com/gaprite/introduction.html Retrieved: 10/12/10

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: http://www.howtodothings.com/automotive/a3235-how-to-calculate-your-braking-distance.html Graph image from: http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway/forces/motionrev3.shtml Retrieved 10/12/10 Speed of a car in miles per hour

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: http://www.bigfoto.com/miscellaneous/photos-04/index.htm Chart image from: http://www.dailykos.com/story/2009/8/20/770104/-Will-You-Knock-Off-The-A**hattery-Out-There Retrieved: 10/13/10

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.

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: http://www.independentmail.com/photos/galleries/2009/jul/24/motor-home-accident-abbeville-highway/18156/ Small skid image from: http://www.knoxandassociates.com/accident.php Retrieved: 10/13/10

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 0.039 (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: http://www.theradioroom.org/RandomImages.htm Retrieved 10/13/10

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: http://www.driversedguru.com/drivers-ed-training-exercises/stage-4/stage-4-driving-in-hazardous-conditions/ Snow image from: http://www.mlive.com/news/index.ssf/2009/01/storm_heading_into_northeast_l_1.html Retrieved: 10/12/10

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

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: http://hyperphysics.phy-astr.gsu.edu/hbase/crstp.html Retrieved: 10/12/10

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: http://bikeportland.org/resources/bikesafety Retrieved 10/12/10

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: http://knowledge.allianz.com/en/globalissues/energy_co2/top_climate_stories/key_2008_cars.html Retrieved: 10/13/10

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 Silver car image from: http://www.northescambia.com/?p=6365 Teal car image from: http://www.educationforthedrivingmasses.com/2008/06/christopher-robbins-17-of-cambridge.html Brown car image from: http://fugitive.com/archives/tag/brennan-s-eden-car-crash

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: http://www.northescambia.com/?p=10880 Truck image from: http://www.syracuse.com/news/index.ssf/2009/09/pickup_crushed_after_headon_cr.html Retrieved: 10/13/10

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: http://cars.uk.msn.com/news/articles.aspx?cp-documentid=147862860 Red/brown images from: http://scienceblogs.com/dotphysics/2009/02/lighter-but-strong-cars-still-dangerous.php Van image from: http://www.cars.com/go/crp/buyingGuides/Story.jsp?section=Van&story=2007minivanSafe&subject=stories&referer=&year=2007 Retrieved: 10/06/10

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: http://www.thesun.co.uk/sol/homepage/motors/237410/Dont-risk-your-childs-life.html Ad image from:http://marginalizingmorons.blogspot.com/2009/04/massachusetts-dumbest-state-qed.html Retrieved: 10/01/10

Speed & Braking PSAs Click on web address to access video clips TAC Victoria “Slo-Mo” Speed & Braking Collison http://www.youtube.com/watch?v=SuY_VHzKdjc (1:00) THINK! Slow-Motion Braking Collision http://www.youtube.com/watch?v=mDWCen_09o8 (0:30) Spain DGT Speed & Braking Rear End (in Spanish) http://www.youtube.com/watch?v=SYb9rpAziU0&p (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: http://www.youtube.com/ Retrieved: 01/21/10

Speeding & Crashes PSAs TAC Victoria Wipe Off 5 (Hit Pedestrian) http://www.youtube.com/watch?v=5Z23CzSONiU (1:01) THINK! 5mph Over (Hit Pedestrian) http://www.youtube.com/watch?v=Qm8yyl9ROEM (0:30) Transport Safety The Faster You Go The Bigger the Mess (Rear End & Pedestrian) http://www.youtube.com/watch?v=8ZtdP3HNUpo (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: http://www.youtube.com/ Retrieved: 01/21/10

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

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

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