AAA KentuckyDriver Training

Introduction• 50 - 60 decisions/mile (@60mph 1 per sec)• Decisions relate to adjusting time, space,

and visibility within the limits of available traction for operating conditions (law, other users, road environment, risk)

• Experienced driver relies on driving habits• Safe driving habits alter risk in a positive

manner

Introduction(2)

• A safe driving career requires driving habits that encompass proper attitude and proper skill

• To accomplish this, an individual must acknowledge risk, understand the driving process, and desire to constantly strive for improvement

Introduction(3)• Habit development

– Know what to do– Have a desire to do it– Demonstrate that you can do it– Overcome resistance to change– Understand correct, or incorrect, performance– Practice correctly at least 25 times– Ability to do correctly without conscious thought

Introduction(4)

• Classroom presentation provides the basic knowledge

• BTW demonstrates the process

YOU MUST PROVIDE THE ATTITUDE AND THE DESIRE TO CONSTANTLY IMPROVE!

Dynamics of Driving

• Vehicle Response

• Human Response

Natural Forces Affecting Driving• Gravity (the pull of earth's mass on object's at or

near earth's surface)• Friction/Traction (resistance to motion between two

bodies in contact)• Kinetic Energy (energy associated with mass and

motion)• Impact, i.e.. transfer of energy (absorption of kinetic

energy with the release of other forms of energy)• Inertia (objects at rest or in motion will remain at

rest or in motion until acted upon by an outside force)

Dynamics of Driving

• Driver controls speed and placement through use of

• Brakes (slows/stops tire rotation against road)• Accelerator(causes drive wheels to rotate against road)• Steering(front wheels turn and rotate causing direction

change)

Vehicle Response• Every control input

depends on the tire/driving surface interface

Courtesy of Goodyear and ADS

Vehicle Response• The effectiveness (time/distance) of each

control input depends on Newton’s Laws of Motion

• You can’t beat natural law, regardless of age, reflex, or skill!

• You must allow for the effect!

Vehicle Response• The tire/driving surface interface is referred to as friction, or traction• Friction is the horizontal force required to move an object (F) divided by the weight of the object (w).• Friction is influenced by

• Surface type (asphalt, concrete, dirt, grass, gravel)

• Surface contour

– Slope(+/-)

– Curve (horizontal vs centrifugal / bank)

• Surface condition (wet, oil, leaves, snow, ice, standing water)

wFf

Vehicle Response• Weight Shift

• During a stop

• During acceleration

• During a turn

Inertia Effect

Vehicle Response• When turning if inertia overcomes the

friction content of the surface the vehicle leaves its intended path

• Locked wheels: Vehicle continues in direction it is heading regardless of steering input- reduce speed before the turn!

Inertia Effect

When cornering, tires tend to fold.

Underinflated, contact with the rim will be lost. (AIR LOSS MAY OCCUR)

Vehicle impacts solid object at 35mph, it begins to crush and slow down (transfer of energy).

Each inch of crush dissipates about 1 mph of energy. Body continues forward at 35 mph (inertia).

Vehicle stops in 1/10 sec., body impacts 1/50 sec later, body stops in 1/100 sec.

Vehicle impacts solid object at 35mph, it begins to crush and slow down (transfer of energy).

Belted body tends to keep moving forward but belt retards forward motion.

Seat belts are fastened to vehicle frame allowing body to decelerate with vehicle collapse. Air bag further retards forward motion. Time for body to stop reduced from 1/100 sec to less than 1/10 sec.

Vehicle ResponseRelationship of Kinetic Energy, Mass, & Speed

Vehicle Response• Energy increase = the square of the speed

increaseKinetic Kinetic X speed X energy

MPH energy MPH energy increase increase15 15017.394 to 30 60069.578 2 415 15017.394 to 45 135156.55 3 915 15017.394 to 60 240278.31 4 1615 15017.394 to 75 375434.86 5 25

Damage and injury increase in proportion to the energy involved in a crash

1501799.21)2.322000(5.5. 22 mvKe

mphfpswgKev 15/99.212000

15017)2.32(22

11.622.322000 g

wm

Vehicle Response• Braking distance increase = the square of the speed

increase

BrakingBraking Braking X speed Distance

MPH Distance MPH Distance increase increase15 10 to 30 40 2 415 10 to 45 90 3 915 10 to 60 160 4 1615 10 to 75 250 5 25

ftfSdBRAKE 10)75.0(30

1530

22

f = 0.75 dryf = 0.45 wetf = 0.20 ice

Braking distance does not include PRT distance

Vehicle Response

24.0

0'15

.00'

21.0

0'

Time required to accelerate

sec03.415.0)1524(25.0 f

dt

The gap to enter traffic, or cross an intersection, depends upon the rate of travel of oncoming traffic.

Use a safety margin!

Turning: Critical Speed

mphefrS 42.2075.0

21)(87.3

Critical speed is the absolute maximum speed at which a vehicle will travel a specified turn radius (stay in its intended path) with a given friction value.

Do not attempt a normal intersection turn in excess of 10 to 15 mph!

Human Response• Perception/reaction time has 5 components

• Search• Identify• Predict• Decide• Execute

PRT is the time it takes to recognize and react to a

hazard.

Human Response• Average PRT is 1.5 seconds• During PRT a vehicle travels at a constant speed• PRT is increased by

• complexity of situation• choice of available actions• distractions• alcohol/drug impairment• age

Stv 466.135mph = 51fps55mph = 80.63fps65mph = 95.29fps

Total Response Time

355565

76.65ft 54.44ft 131.09ft120.45ft 134.44ft 254.89ft

142.35ft 187.77ft 330.13ft

f = 0.75 dry

f = 0.45 wet

f = 0.20 ice

76.65ft

76.65ft

76.65ft

54.44ft 131.09ft

90.75ft 167.4ft

204.166ft 280.8ft

Total Stopping Distance from 35mph - various conditions

PRT distance + Braking distance = Total Stopping Distance

ftStdPRT 65.765.1)35(46.146.1

ftfSdBRAKE 44.54)75.0(30

3530

22

ftddd BRAKEPRTTSD 09.13144.5465.76

Stopping & Space Cushion

MPH FPS ReactDist

BrakeDist

TotalDist

Spacefeet

Cushiontime

15 21.99 32.98 10.00 42.99 44 [ 65] 2 [3]

25 36.65 54.97 27.78 82.75 74 [110] 2 [3]

35 51.31 76.96 54.44 131.41 103 [154] 2 [3]

45 65.97 98.95 90.00 188.96 132 [198] 2 [3]

55 80.63 120.94 134.44 255.39 323 [245] 4 [3]

65 95.29 142.93 187.78 330.71 382 [286] 4 [3]

React Dist + Brake Dist = Total Stop Distance

React time = 1.5 sec Friction = 0.75

The Safe Driver

• A safe driver controls risk by managing time, space, and visibility within the limits of available traction.

» Steve Bail

Driving Instructor

AAA Kentucky

Becoming a Safe Driver• Learn to handle vehicle competently

through range of maneuvers & conditions• Recognize & identify hazards and handle

successfully• Keep adequate space margins• Maintain proper speed for conditions

To obtain these objectives a driver must learn and use …...

Proper Visual Habits