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Module 3 Topic 1: Laws of Nature Topic 2: Vision and Driving
Topic 3: Vehicle Reference Points and Establishing Lane Position Topic 4: Basic Maneuvering—Steering, Braking and Vehicle Balance
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Topic 1 How Laws of Nature Affect Vehicle Balance & Weight Load Transfer
Gravity Kinetic Energy Momentum Inertia
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Gravity Gravity is the natural force that constantly pulls all things to the earth and affects an object’s weight. Center of Gravity is a point where the mass of the vehicle is concentrated and balanced. The higher the center of gravity, the more unstable the vehicle becomes. When a driver brakes, accelerates, or corners, the G forces are amplified. Natural laws are physical forces that influence the movement, balance and weight of your vehicle. Gravity is the natural force that constantly attracts objects toward the center of the earth; The weight of an object is a result of the mass of the object multiplied by the standard gravitational force, (which, for an object in free-fall, is 9.8 meters per second squared). Therefore, mass is different from weight: if a ball has a mass of 1 kilogram on Earth, it will have the same mass (1 kg) on the moon; however, the ball would weigh six times more on the Earth because Earth has a stronger gravitational force than the moon. Examples of Gravity: If you throw a ball into the air, gravity will eventually cause the ball to fall back towards the earth; If you ride a sled down a snow-covered hill, gravity is the force that allows the sled to continue moving down the hill until it levels out without any additional propelling force; If you park on a flat surface, gravity is acting on your vehicle by keeping it anchored to the ground, preventing it from floating away; The G forces acting on the vehicle are amplified, when a driver brakes, accelerates, or turns, increasing forward pitch, rear pitch, and roll, respectively; Center of Gravity: a point where the mass of a body is concentrated and, if suspended at that point, would remain balanced. Vehicles are designed to have a low center of gravity in the vicinity of the passenger compartment The lower the center of gravity, the more stable the vehicle is, and the less likely it is to roll; A vehicle’s center of gravity becomes higher when loaded with passengers and cargo A vehicle’s center of gravity becomes chassis components are above the axles, the higher the center of gravity will be for that vehicle. Question: Name some types of vehicles that have a lower center of gravity; Possible Answers: any type of sports or race car Question: Name some types of vehicles that have a higher center of gravity: *NOTE* While SUV’s may technically have a higher center of gravity, advances in technology have enabled electronic stability systems that can prevent some of the conditions that lead to roll-overs. Possible Answers: Semi-trucks, Jeeps, Box-Trucks or Vans, Pick-up Trucks with raised suspensions SUVs* Factors that Affect the Rate and Impact of a Vehicle’s Load Transfer Weight distribution Center of mass Inertia Suspension Tires and wheels Axle Track and Wheelbase Aerodynamics Electronic Stability Control (if equipped) The Driver: how hard and how suddenly the driver brakes, accelerates, or turns the steering wheel
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Kinetic Energy The Energy of Motion
Kinetic energy is the energy an object possesses due to its speed, or velocity. The faster the object moves, the more energy it collects. A heavier moving object will have more kinetic energy than a lighter object moving at the same speed. A vehicle’s kinetic energy can be overcome by brakes, friction, air resistance and gravity. The amount of kinetic energy an object has is based on two variables: the mass (m) of the object and the speed, or velocity (v) of the object. Kinetic energy is directly proportional to the square of its speed, therefore the faster an object moves, and the more mass an object has, the more kinetic energy it has. The mathematical equation for kinetic energy is KE = 0.5 x m x v2 The standard metric (SI) unit for measuring kinetic energy is the Joule, (symbol: J); the Joule is equal to the energy transferred (or work done) by a force of one newton when its point of application of force of 1 newton is displaced through a distance of 1 meter in the direction of the force. Using the United States customary and imperial units of measure, kinetic energy is measured by the foot-pound, (symbol: ft∙lb); one foot-pound equals the energy transferred upon applying a force of one pound-force (lbf) through the displacement of one foot. One Joule = foot-pounds. One foot-pound = Joules A massive moving object will have more kinetic energy than a less massive object moving at the same speed. Example: a freight train moving at 45 mph has much more kinetic energy than a mid-size sedan moving at 45 mph. Example: A massive SUV with two people and the cargo area filled with luggage will have more kinetic energy than a less massive compact car with the same two people and luggage. Since it is impractical or impossible to measurably change the mass of a vehicle while in motion, you can only overcome the vehicle’s kinetic energy (i.e. slowing/stopping the vehicle) by lowering its velocity (i.e., your speed). Multiple outside forces can act on your vehicle to hinder or lower its velocity, for example: The Driver engaging the brakes Friction (i.e., traction between tires and the road) Air Resistance Gravity
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Momentum Momentum refers to the quantity of motion an object has.
Change in momentum is called impulse; the magnitude of impulse is based on the amount of opposing force and the timespan over which that force is applied. Question: Why do airplanes need a long runway before taking flight? Why do pole vaulters take a running start before using the pole to catapult themselves over the bar? Why do skiers travel downhill for period of time before going over a jump? Answer: Because they all need to increase their velocity to build up enough momentum to overcome all forces that want to keep them stationary in order to become airborne. Momentum, (symbol: p) refers to the quantity of motion that an object has; The SI unit for measuring momentum is the kg ∙ m/s To determine the amount of momentum an object has, multiply the object’s mass by its velocity: p = m ∙ v. This formula shows that an object’s momentum is directly proportional to both the object’s mass, and its velocity. Since all objects have mass, whenever an object is moving, it has momentum; whenever an object is at rest, (i.e., v = 0), it has no momentum because no matter what its mass is, its velocity is zero and any number multiplied by zero equals zero. Since the amount of mass a vehicle has is directly proportional to the amount of momentum, larger objects have more momentum at a lower speed than smaller objects going the same speed: Example: it’s easier to stop a marble rolling at 10 mph than it is to stop a bowling ball rolling at 10 mph To increase the momentum of a vehicle, you must apply a net force on the gas pedal that is greater than that of the forces working against it (gravity, air resistance, mass of the vehicle, etc.); the resulting imbalance in forces will cause your vehicle to accelerate, increasing in velocity; To decrease the momentum of a vehicle: Take your foot off the gas pedal/ turn off cruise-control), apply a net force on the brake pedal that is greater than that of the forces working to keep the car moving (inertia, momentum, kinetic energy, etc.); the resulting imbalance in forces will cause your vehicle to slow and/or stop, decreasing velocity; Change in momentum is called impulse; the variable in almost any scenario is going to involve a change in velocity, not mass. With driving, impulse refers to the degrees of force the vehicle experiences when changing momentum. Impulse = Force of Impact ∙ Time of Impact Force of impact = Force of Contact: The force of the contact between your vehicle and the opposing force (how hard you hit the brakes, how heavy the vehicle that t-boned you was, how sturdy the fence you ran into was, etc.); Time of Impact = Time of Contact: The duration of the time-span over with the force of contact was applied (how suddenly you braked, how fast a car that t-boned a truck was going, etc.; A large amount of force applied for a very brief amount of time creates strong impulse. Example 1: Babe Ruth’s baseball bat connecting with the baseball on a home-run hit. Example 2: A large vehicle going 60 mph hitting a telephone poll A small amount of force applied over a very long period of time creates minimum impulse. For Example: A hiker using snow shoes to slowly creep across a think patch of ice is an example of minimizing impact so that his/her body does not exert more force than that of the ice beneath him/her—which would result in the hiker falling through the ice. Question: If a dump truck and a compact car are both moving at 50 mph, which vehicle has more momentum? Answer: The dump truck, because it has more mass. As momentum increases, so does the potential for increasingly severe damage in a collision. The people inside of a vehicle have the same momentum as the vehicle, but they are not subject to outside forces that will decrease the vehicles speed (e.g., the friction between the brake pads and the tires, the friction between the tire and the road, or an object/vehicle with which the car collides. The people inside the vehicle must rely on the vehicle’s crumple zone, seatbelts and airbags to reduce their momentum in concurrence with the vehicle’s reduction in momentum, or they will continue to move forward (and potentially through the windshield).
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A Vehicle’s Possible States of Motion
Inertia Inertia: an object’s tendency to resist any change in its state of motion. Slowing down or Stopping Accelerating or Cruising Turning towards the Left Turning towards the Right A Vehicle’s Possible States of Motion Answer to Question on Slide: After slowly and steadily chugging up a steep track the rollercoaster cars and people in them come to almost a halt at the apex of the track’s arch, then as soon as the car passes that point, the rollercoaster rapidly accelerates, giving people the sensation of being “left behind,” as in the cartoon above the question. Newton’s First Law of Motion aka The Law of Inertia: “An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction until acted upon by an unbalanced outside force.” Inertia is the tendency of any physical object to resist any change in its state of motion, that is, the object’s speed and direction; The amount of mass of an object has is directly proportional to the amount of inertia it has. This means the more massive the object, the more inertia it has. The more inertia an object has, the more resistant it is to changing its state of motion. Therefore, the more massive the object, the harder it will be to slow it down, stop it, get it moving, increase speed, turn left or turn right. Example: it is easier to stop a marble rolling down a ramp at 4 mph than it is to stop a bowling ball rolling down a ramp at 4 mph. Vehicle occupants feel the effect of inertia when the driver applies the brakes or steers through a curve Braking causes occupants of the vehicle to fall/move forward because inertia wants keep the body moving; the body stops moving forward as a result of outside forces such as seatbelts, crumple zones, airbags, and the vehicle’s shell. Turning the steering wheel for the curve causes occupants of the vehicle to feel like they are being pulled toward the outside of the curve because inertia wants the occupant’s bodies to keep moving in a straight line; the bodies move through the curve with the vehicle to Inertia will keep the body moving in the original straight line The vehicle provides the external force to the body so it will move through the curve with the vehicle Occupant restraints provide external force to keep the occupants securely in their seats
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Controlling Vehicle Balance Changing the Vehicle’s Center of Gravity
What transfers weight from one point of the vehicle to another? Acceleration Deceleration/Braking Steering Input/Cornering Surface Traction Automobile Chassis Vehicle Balance: The frame that your vehicle sits upon is called the “chassis,” and you have a tire located at each of the four corners. When parked on perfectly level ground, the weight of your vehicle should be concentrated at the center of the chassis; that is, the weight is equally distributed across all four tires. Vehicle balance refers to the distribution of the vehicle’s weight on all four tires. Ideal balance and maximum tire contact with the ground is only reached when vehicle is motionless; even at a full stop, each tire has a patch only the size of a dollar bill in contact with the ground. The part of the tire in contact with the ground is what gives your vehicle traction. Review Question: When a vehicle is parked on level ground, how big is the area of the patch of each tire that is actually in contact with the ground? Potential Answer: Each tire has a patch about the size of a dollar bill in contact with the ground, or about 15 square inches (a dollar bill is roughly 2 and ½ inches x 6 inches). Vehicle Balance (continued): Maintaining your vehicle’s balance is critical to keeping control of your vehicle, and the magnitude of the weight shifts between the tires can be affected by any combination of factors: Rate of Acceleration: how much pressure you apply to your acceleration pedal at one time, or, “how fast you go faster.” Rate of Braking: how much pressure you apply to your brake pedal at one time or how hard you brake. Steering Input: the direction and degree with which you are turning. Surface Traction: how much grip your tires have on the road which is affected by: Weather: rain, snow, or any other kind of precipitation will decrease the amount of traction; Road Surface: Dry, well-maintained asphalt roads usually provide the most traction; Asphalt becomes slick when it first begins to rain or when it rains so hard or so much that the road retains standing water, (sometimes imperceptible to the eye), and puts you in danger of hydroplaning; Leaves or pine needles covering the asphalt can also cause a loss of traction; Dirt, slate, and stone roads can become very slippery where gravel is loose or piled up. The photo on the lower right side of the slide shows a vehicle losing traction with its rear wheels while making a sharp turn on a loose, dusty gravel road. Condition of your tires: you must monitor the tread on your tires for wear and tear to maintain maximum stopping and steering power. Review Question: How can you tell if your tires have enough tread? Potential Answer: If the tread reaches the top of Abraham Lincoln’s head when you place a penny in the groove. The suspension system is comprised of springs, shock absorbers, and links that connect the main body of the vehicle to the chassis and its wheels, allowing relative motion between the two and across the frame of the vehicle. There are the three weight transfers you must balance in order to maintain maximum stability in your vehicle: roll, pitch, and yaw. Questions (refer to photos at the bottom of the slide): Question 1: Pitch (photo on far left) Describe where the vehicle’s weight load is concentrated in this picture. What might the driver have been doing to cause this shift in weight load? Answer: The weight has shifted to the rear tires. The driver appears to be quickly accelerating. Question 2: Roll (center photo) Describe where the vehicle’s weight load is concentrated in this picture. What might the driver have been doing to cause this shift in weight load? Answer: The vehicle’s load has almost entirely shifted to the tires on the right side. The driver appears to have been making a hard right turn without braking on the way into the turn. Question 3: Yaw (photo on far right) Describe where the vehicle’s weight load is concentrated in this picture. What might the driver have been doing to cause this shift in weight load? Answer: The weight has shifted to the rear right tire. The driver appears to be braking to make a hard left turn from a high speed on a loose gravel driveway. Pitch Roll Yaw ©Virginia Department of Education
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Controlling Vehicle Balance Pitch
Vehicle Shifts Weight from Front to Rear or Rear to Front Changing Weight From Rear to Front Release Gas Pedal Brake Changing Weight from Front to Rear Release Brake Accelerate Forward Pitch Backward Pitch Forward Pitch Answer to question on bottom right side of the slide: “B,” the driver is accelerating rapidly causing the front end of the truck to lift and the weight to shift to the rear tires. Pitch “Pitch” describes the transfer of vehicle weight front either the front to rear, or rear to front. Question: Think about an action movie scene where the driver must speed up a ramp and get enough momentum to sail through the air over an impossibly wide river and to get safely to the other side, but despite being a bumpy getaway, she makes it. How does the vehicle move when it lands? Answer: The front tires land first, then the back tires hit and if the jump was high enough, the front tires may even rear back up off the ground. That is a very extreme example of “pitch.” In real life, pitch is usually much more subtle. Normal pitch (that does not involve using ramps to jump over rivers) occurs: When the driver releases the brake: simply taking your foot off of the brake pedal when you are in “Drive” in an automatic transmission vehicle will cause at least a slight shift in weight to the front tires. If you are on flat ground or a hill, your car may even begin to roll forward. When the driver slams on the brakes, the vehicle pitches forward and the majority of the vehicle’s weight suddenly transfers to the front tires. Question: What happens to a book on the passenger seat when the driver suddenly slams on the brakes? Answer: The book will slide off the passenger seat and onto the floor in front of it. Question: How does the vehicle weight transfer when the driver slams on the brakes? Answer: When the driver hits the brakes, the car pitches forward, causing the majority of the weight to shift to the two front tires. You can shift the weight of your vehicle from the front suspension to the rear suspension by: Releasing the brake: take your foot off of the brake pedal; you should never have the brake pedal and the accelerator pedal pressed at the same time. If you want to move forward, stop, “stopping.” Covering the accelerator: pivot your foot so it’s hovering directly above, but not touching, the accelerator pedal. As you feel the vehicle start to shift forward, gently make contact with and apply pressure to the pedal; Applying light pressure to the accelerator: to maintain balance while maintaining slow forward motion or reducing speed gradually with minimal weight shift (the greater the weight shift, the more noticeable and uncomfortable it will be). Progressively applying pressure: to the accelerator firmly and steadily to increase speed and gradually shift the balance of the vehicle to the rear suspension; this eases steering control and improves rear wheel traction when moving out of a turn or curve. Thrusting pressure on the accelerator: A firm push of accelerator used to shift more weight to the rear wheels for traction or to cause a shift to a lower gear in a vehicle with an automatic transmission to increase the rate of acceleration. This process is sometimes needed when passing or changing lanes in higher speed traffic situations. It takes experience and practice to learn the ability to apply the correct amount of pressure on a vehicle’s brake pedal to get the vehicle to stop smoothly and efficiently. Additionally, the “correct amount” will vary between vehicles by year, make, model, and condition of the vehicles’ braking systems. *Review Question: Think back to when we talked about how to and why you should maintain your vehicle. Name and discuss the four factors that can influence the amount of wear and tear on the brake system: Possible Answers: 1). The number of miles the vehicle has been driven; 2). The type of miles (stop-and-go/city traffic, country roads, interstate highways); 3). The nature of the terrain covered (e.g., mountains, lowlands, etc.); and 4). The driver’s habits (aggressive drivers tend to wear out their brakes faster) You can shift the weight of your vehicle from the rear suspension to the front suspension by: Releasing pressure on the accelerator pedal: simply releasing pressure on the accelerator results in a shift of weight to the front. The affect on the reduction in speed tends to be more noticeable in vehicles with rear-wheel-drive than in front-wheel-drive vehicles equipped with transaxles. Covering the brake: pivoting your foot so it hovers just above the brake pedal is called “covering the brake” and it helps provide a smooth transition from acceleration to braking. It is similar to trail braking in that the speed and vehicle balance are maintained prior to braking. Controlled braking (Squeeze On): Apply sufficient pressure to the brake pedal to slow your vehicle down to your target speed while maintaining balance to avoid traction loss to front or rear wheels. Controlling the direction of your vehicle becomes much more difficult when you are slamming on your brakes. Threshold braking: Threshold braking maximizes the braking effect of the vehicle by lifting weight off of, (unloading), the rear suspension and lowering the weight onto (loading) the front suspension to provide the maximum amount of traction to the front tires just short of locking them up. If the tires do lock up, regain control of your steering by releasing brake pressure very slightly (2-3 degrees). Maintain control of how much pressure you exert on the brake pedal by keeping your heel on the floor. Trail braking: Trail braking is used to maintain speed and balance of the vehicle when steering is required prior to turning at an intersection or in a curve. This technique is often used in combination with or at the end of controlled or threshold braking. Backward Pitch Slowing down shifts weight to front tires Speeding up shifts weight to rear tires
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Controlling Vehicle Balance
Roll - Vehicle Shifts Weight from Side to Side Three Factors that Factor in Creating Vehicle Roll: Steering Wheel Movement: Sudden jerky steering will throw the vehicle’s weight to the inside tires of the direction you steer. Brake Application: Certain braking/steering combinations can be used to minimize roll while navigating a sharp or long turn. Grade of the Road: Although interstates are mostly flat, smaller roads sometimes slope downward on the sides with the highest point in the middle. Roll Think back to (or re-watch) the video clip in Slide 56, demonstrating the push-pull-slide steering technique. How does the vehicle’s weight shift as the driver maneuvers through the cones? Roll refers to the transfer of vehicle weight from the tires on the towards the outside of the turn. Rolling your vehicle is dangerous and potentially fatal. It occurs when the weight of the vehicle shifts to the left or right side. Weight, or “center of mass” shifts to left or right side of vehicle depending on speed, traction, and amount of steering input. Occupants may or may not feel forward lifting movement from the corner of the vehicle opposite the direction of the turn. This is because as you begin to steer into a curve, the vehicle’s weight shifts to the tires on the inside. The driver must balance the speed of the vehicle against the transfer of weight to the outside tires causing roll. Brake and Steering Combinations: Depending on the degree of steering and brake input, braking at certain points may improve traction, such as in “trail braking” through a turn, when performed at an appropriate speed. However applying the brakes when cornering at too high a speed has little effect on slowing the vehicle down, but may have a very noticeable effect of producing traction loss due to severe weight shift to the front tire on the inside of the curve. When going into a turn if you accelerate the weight transfers to the outside front tire and if you brake coming out of it the weight transfers to the outside rear tire: this means the vehicle’s center of gravity is disproportionately thrown to the outside of the vehicle and puts it in danger of rolling. Tall, narrow and top-heavy vehicles are more susceptible to roll.
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Controlling Vehicle Balance Yaw
Vehicle Rear-Load Transfers to the Left, Right, or Back and Forth Factors that Affect Rear-Load Transfers to the Right/Left: Sudden braking Sudden/excessive acceleration Sudden/excessive steering Traction loss to either the left or right rear tire Road is tilted to either the right or left Yaw Yaw describes the transfer of the vehicle’s weight when the rear-end swings to the right, to the left, or back and forth (also known as fishtailing), in extreme cases of control loss, the car can go into a complete spin covering 360+ degrees. What Causes a Vehicle’s Rear Load to Shift Left, Right, or Back and Forth? Suddenly braking: when you brake suddenly and forcefully, the vehicle’s weight shifts to the front tires, reducing the amount of friction (i.e. traction) the rear tires have with the road; Sudden or excessive acceleration: especially in a rear-wheel drive vehicle’s with powerful engines, if the engine provides more power than the tires can transmit the wheels will lock up; Sudden or excessive steering: when you make a sharp turn at a high speed, the vehicle’s rear will swing opposite the direction in which you are steering; if you find you’ve steered too sharply and suddenly, forcefully steer the other direction the vehicle will skid to the other side in a fishtail; Traction loss to either the left or right rear tire: especially common on icy, slippery, or loose gravel roads; Road tilted to either the right or left: country roads and highways are not built to the same specifications as interstates and may have sharper curves or uneven grading; The driver most offset the skid by steering the front wheels in the same direction as the skid and reducing engine power. You must only steer as much as needed to offset the skid or you will overcorrect and cause the vehicle to skid in the other direction (fishtailing). Two-wheel drive pick-up trucks that are not carrying a load in the back are more prone to problems with maintaining balanced yaw during icy or slippery conditions; with less weight centered over them, the rear tires may lose traction and the rear end of the vehicle may skid to one side other, or back and forth (fishtailing).
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Topic Two Vision and Driving
Your eyes are the most important source of information when you are driving. In this topic, we will learn about: “Visual perception” as a skill that needs practice and time to develop The importance of clear attentive vision while driving The type of information that is relevant to us, as a driver The human field of vision Factors that affect visual perception
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Vision and Perception Vision Perception
The eye’s ability to distinguish the number, shape, and color of an object. Perception How we interpret and understand information gathered by any of the five senses. Your ability to drive safely is affected by how skillful you are at using your vision to accurately and effectively perceive your surrounding, ever-changing environment while you’re driving. For our purposes: Vision is the ability of the eyeballs to distinguish shapes and colors. Personal factors that affect vision include: Visual acuity: (how good your eyesight is), affects how clearly you are able to see/read things up close and far away Height: may affect what you see, how far in the distance you can see Eye health: many health conditions can affect the eyes, including pink eye, cataracts, diabetes, and glaucoma Ability to see color: Up to 10% of males and 1% of females in the United States have some type of color-blindness, the most common of which is the inability to see the colors red and green. Environmental factors that affect vision include: Distance Atmospheric visibility Terrain Speed Perception is how people organize, identify, and interpret information gathered by the five senses to represent and make sense of the objects, events, and processes present/going on in the world around them. Perception is subjective—meaning that perception varies from person to person, Our individual perceptions are based-on or influenced-by many factors, including: Culture—the culture(s) one: grew up in; currently embraces; has been exposed to; Education—level, type, quality, concentration of subject matter Experiences—type, variety, age, level of impact Emotions—intensity, type, cause Opinions —intensity, knowledge of subject, relation to personal values Visual Perception is the ability to interpret the surrounding environment by processing and interpreting the information gathered from what you see. Visual perception also varies from person to person based on numerous factors, both personal and environmental: Question: Using only your vision, [exclude your perceptions] describe the graphic labeled “Figure 1” at the bottom right of the slide. Possible Answers: four, evenly-sized hearts, each with a line down its center, that join together by meeting at the “points” of the heart shapes; this formation of hearts sits atop a slightly curved line segment; the outline of the full shape is a consistent shade of dark green; the color of the heart shapes themselves gradate out from the center from dark green to lighter shades of green with a hint of yellow towards the very top edges. There is an oval of light grey around, but not overlapping the slightly curved line segment emerging from between the bottom two heart shapes. Questions: Now, describe your visual perception of that graphic (Figure 1 at the bottom right of slide). What is it called? plant; weed, shamrock; computer graphic; four-leaf clover; cartoon drawing, animated; What does it mean? In American popular culture, four-leaf clovers symbolize good luck/good fortune; What do we associate with it? Spring; Irish/Ireland; good luck; rarity; St. Patrick’s Day; How do we perceive its size, dimensions and proximity? The grey oval behind the stem of the shamrock and the color gradation of the leaves represent the shadow and depth of the object, creating the illusion that the shamrock is three-dimensional; however, because you know that, in reality, it is a computer animated image of a shamrock projected on the screen and is two-dimensional.
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What do you see? Click Once to bring up the question, “What do you see?” Instruct the students to watch the PowerPoint screen; Click Again to bring up the optical illusion image and instruct your students to call-out or write-down what they immediately see. Question: This is an optical illusion drawing: what is the first thing you see when it appears? Possible Answers: Duck or Rabbit
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Your Eyes are Critical to Driving
About 90% on what they see. About 10% of all on what they hear or feel. Drivers Base Driving Decisions on: Search at least 20 seconds ahead in your path of travel to evaluate the situation and make good decisions about speed, lane position, signs, signals, markings, and potential hazards. Drivers:
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What Kind of Visual Input is Relevant to the Driver?
Information that could affect how you navigate your path of travel. What they are expected to do. What they are prohibited from doing. Changes in road/lane structure. Potential hazards. Location of common public destinations. Signs, Traffic Signals, and Lane Markings inform drivers of: We are constantly being bombarded by a massive amount of visual input from the world around us. Part of becoming a good driver is knowing what to look for—you must develop the skill to sort through the massive amount of information your brain is receiving from your eyes, and then determine: Which information is relevant? (information that dictates or could potentially affect your path of travel and how you navigate it; What, if any, action(s) does the information require? ( How you should adjust the vehicle’s speed, position or direction to continue safely and legally through your path of travel to your target). Searching Road Conditions and Potential Hazards What should the driver be paying attention to and why? Signs, Traffic Signals, and Lane Markings that inform drivers of: What they are expected to do: when/where to stop, go, turn, merge; (Stop sign; green traffic light; lane painted with a white turn arrow and “only”) What they are prohibited from doing: driving direction, speed, and maneuvers (Speed Limit sign; red traffic light; double yellow line) Changes in road/lane structure: (Divided Highway sign; blinking yellow light; converging lane lines; Potential hazards: Deer Crossing; Slippery Road; Yield, Pedestrian Crossing, Children at Play; lighted signs warning of “Road Work Ahead” or “Fog on Mountain” Location of common public destinations: Hospitals; Airports; Rest Areas Surrounding driving environment and potential hazards, including Relative location, direction and speed of other vehicles: prevent collisions by watching for stopped, turning or braking vehicles; Displays of aberrant behavior by other drivers: rapid lane changing, weaving, abuse of car horn, etc. may indicate a driver who is distracted or impaired by anger (road rage), distractions (texting), fatigue, or alcohol use Weather and road conditions: high wind gusts, fog, rain, black ice, standing water, slick areas Actual presence of pedestrians, bicyclists, children, animals or areas where they are likely to be: crosswalks, sidewalks, bike lanes, playgrounds, deer crossing areas ©Virginia Department of Education
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What Kind of Visual Input is Relevant to the Driver?
Information that could affect how you navigate your path of travel. Relative location, direction and speed of other vehicles. Displays of dangerous behavior by other drivers. Weather and road conditions Presence of/areas where. pedestrians, children, and animals may be. Surrounding Driving Environment and Potential Hazards We are constantly being bombarded by a massive amount of visual input from the world around us. Part of becoming a good driver is knowing what to look for—you must develop the skill to sort through the massive amount of information your brain is receiving from your eyes, and then determine: Which information is relevant? (information that dictates or could potentially affect your path of travel and how you navigate it; What, if any, action(s) does the information require? ( How you should adjust the vehicle’s speed, position or direction to continue safely and legally through your path of travel to your target). Searching Road Conditions and Potential Hazards What should the driver be paying attention to and why? Signs, Traffic Signals, and Lane Markings that inform drivers of: What they are expected to do: when/where to stop, go, turn, merge; (Stop sign; green traffic light; lane painted with a white turn arrow and “only”) What they are prohibited from doing: driving direction, speed, and maneuvers (Speed Limit sign; red traffic light; double yellow line) Changes in road/lane structure: (Divided Highway sign; blinking yellow light; converging lane lines; Potential hazards: Deer Crossing; Slippery Road; Yield, Pedestrian Crossing, Children at Play; lighted signs warning of “Road Work Ahead” or “Fog on Mountain” Location of common public destinations: Hospitals; Airports; Rest Areas Surrounding driving environment and potential hazards, including Relative location, direction and speed of other vehicles: prevent collisions by watching for stopped, turning or braking vehicles; Displays of aberrant behavior by other drivers: rapid lane changing, weaving, abuse of car horn, etc. may indicate a driver who is distracted or impaired by anger (road rage), distractions (texting), fatigue, or alcohol use Weather and road conditions: high wind gusts, fog, rain, black ice, standing water, slick areas Actual presence of pedestrians, bicyclists, children, animals or areas where they are likely to be: crosswalks, sidewalks, bike lanes, playgrounds, deer crossing areas
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Want to become a good driver?
You have to spend TIME behind the wheel and actively PRACTICE visual searching skills! “The eyes don’t tell the brain what they see; The brain tells the eyes what to look for.” You must master multiple, complex skill subsets, including visual perception before you become a good driver. As with any skill, it takes a lot of time and practice to master. No one would expect you hit a home-run if you had never picked up a baseball bat before before, no matter how many times you’d watched baseball played; likewise, even though you may have been watching other people drive cars your entire life, you cannot expect to get behind the wheel of a car and automatically expect that you have the requisite skills to drive safely. One of the most important of which is using visual techniques to safely and efficiently guide your vehicle through your intended path of travel. The ability to constantly, effectively, search your field of vision and evaluate how to best guide your vehicle safely through your intended path of travel (without endangering anyone else) is a skill that takes time and practice to develop. When you’re driving, your eyes are being continuously bombarded with massive amounts of ever-changing information and you must train your mind to specifically identify and focus on input that could disrupt your or someone else’s safe path of travel. Questions: What should you be looking or monitoring for while driving? Potential Answers: Traffic signs/signals—examples: stop signs, traffic lights, speed limit signs, double yellow lines, etc. Potential areas of hazard—examples: merge lanes, playgrounds, elementary schools, crosswalks, construction zones, bike lanes, etc. Actual hazards—examples: pedestrians, aggressive drivers, lowered speed limit, falling debris, wildlife, rain, etc. Your vehicle in relation to other vehicles—speed, direction, lane orientation, proximity, etc. Road conditions—examples: traffic congestion, visibility, traction, weather, etc. sdk
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©Virginia Department of Education
Vision 1.5 – 3º in the center of vision field. Allows you to read/see details. Focal Vision 8º in the center of the vision field. Allows you to maintain path of travel. Central Vision More sensitive to light and motion. Orients individual to environment. Peripheral Vision ©Virginia Department of Education
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Field of Vision Area a Driver Can See While Looking Straight Ahead
Viewing Path of Travel Central Vision Focal Vision Targeting (Reading Signs) Peripheral Vision Motion & Color Changes Everything within 180 degrees in front of you
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Visual Testing Visual acuity tests measure the level of detail your eyes can see, (individually, and together), in optimal light conditions. Nearsighted: Able to see near things more clearly than distant ones. Farsighted: Able to see distant things more clearly than near ones.
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Inner and outer sources of concentrated light cause glare.
Lack of light drastically reduces field of vision, visual acuity, depth perception and color recognition. Inner and outer sources of concentrated light cause glare. Nocturnal wildlife become active. People driving at night are more likely to be fatigued. People driving at night are more likely to be intoxicated.
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Seeing at Night: Compensation Strategies
Darkness Drive slower to allow more time to react. Use Focal and Central Vision. Glare Oncoming headlights: Avert your gaze to line painted on right side of road. Internal light: keep it dark in the vehicle when it’s dark outside. Sunbeams: keep windows, headlights, and signal lights clean inside and out. Animals Use your high-beams on rural roads. Pay attention to animal crossing signs. People Watch for erratic driving behaviors from other vehicles on the road. Stay away from drivers exhibiting signs of distraction, intoxication, or fatigue. Darkness reduces your Peripheral Vision to virtually nil; you must use Focal and central Vision to identify hazards and maintain your path of travel. Compensate for the limitations of your reduced field of vision by reducing your speed to allow yourself more time to act Minimize glare: Look towards the white line painted alongside the bottom, right-hand side of the road when oncoming headlights produce bothersome glare; Keep it dark inside the vehicle to prevent glare from internal sources like the dome light, overhead lights, or television/entertainment screen (particularly if situated on the dashboard); Keep your windshield, windows, headlights, signal lights, and taillights clean, inside and out! Dirt and dust on glass not only reduces the ability of your vehicle’s outer lights to illuminate your path and signal driving intentions to others, it will produce glare by reflecting light rather than allowing it to come cleanly, as it would through a clear window Adjust your sun visors to block rays from the rising or setting sun Avoid unwanted contact with wildlife: use your high-beams as often as possible (without blinding other drivers) when driving through the Virginia countryside to increase your peripheral field of vision; look out for signs of animals such as movement alongside the road, the reflection from an animals eyes from your vehicle’s headlights, and road signs that warn of animal crossings. Stay alert and be aware of erratic driving behaviors and stay clear of vehicles that appear to be operated by a distracted, fatigued, or intoxicated driver. Signs of distraction, fatigue, or intoxication include weaving, forgetting to turn on headlights despite it being dark outside, disobeying traffic signals and driving far under the speed limit. Student activity: Before showing the next slide, ask student to list factors other than darkness that affect vision.
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Other Factors that Affect Visual Perception
Glare Fatigue Drugs/Alcohol Weather Darkness Speed Inattention Smoke Age Dirty Windshield Poor Windshield Wipers Poor night vision Night Blindness
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Speed Affects Vision Hazards that increase with increased speed
Drivers have less time to see and react. Minor steering movements cause exaggerated vehicle. movements and weight shift. Speed distorts and reduces peripheral vision up to 90%. Compensation Strategies to use at Higher Speeds Train your eyes to look farther ahead—you’re covering ground faster. Allow more space between your vehicle and others. Actively move your eyes from one side of the path of travel to the other to search for relevant information and hazards. Hazards that increase with increased speed: Drivers have less time to see relevant information and hazards, react, and make good decisions Steering wheel becomes more sensitive to input; even minor steering motions can cause significant weight shift and exaggerated vehicle movements Field of Vision narrows; Fringe and Peripheral vision become blurred and distorted Peripheral vision is reduced tremendously as speed increases: 25% reduction at 30 mph 50% reduction at 50 mph 90% reduction at 70 mph Compensation Strategies to use at higher speeds: Train your eyes to look farther ahead as you increase your speed. Allow more space between your vehicle and others as you may not detect hazards soon enough. Since your field of vision narrows as speed increases, you will need to actively move your eyes from one side of the path of travel to the other, using Focal and Paracentral Vision to search for relevant information and hazards.
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Depth Perception Need both eyes to perceive depth (3D distance).
Allows you to judge gaps, speed, and distance of other vehicles and hazards in the traffic environment. Essential when passing, approaching a vehicle or hazard; turning, merging, and crossing intersections. To judge the distance between vehicles, look at where the tires contact the road, not the body of the vehicle. Depth perception is the ability to judge how far something is, or the distance between two objects. The ability to judge distances between your vehicle and other vehicles and objects is a critical skill and a very difficult task for novice drivers. Left turns are particularly dangerous for new drivers who have difficulty judging gaps between moving vehicles. Question: Ask students when they think they will need to use depth perception? Answer: The ability to judge gaps, speed and distance is essential when passing, approaching a vehicle or obstruction, turning, merging with other traffic, or crossing intersections. Accurate judgment of distance (time and space) becomes more difficult when a vehicle is moving and difficulty increases as speed increases. Examples of how depth perception is used when driving include: Determining following time Entering a safe gap in traffic Stopping behind a vehicle at an intersection Question: How do you learn how to judge distance? Answer: You will learn that you need to look down at the tires in contact with the road, not up at the body of the vehicle. Looking at the tires in contact with the road provides you with a reference point as to where the vehicle is at that moment, and this allows you to judge the amount of pavement between your vehicle and the approaching vehicle. Before going to the next slide ask: “What happens if you have poor depth perception?” Answer: Discuss the list on the next slide.
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Driving Mistakes That Indicate Poor Depth Perception
To compensate for problems with depth perception and judging how far away something is, a driver needs to use reference points and be able to change distance into time. Explain translating distance into time using the 3- to 4-second following distance rule. Explain that each second in that count translates into one car length. Stopping too far from the stop line or intersection. Stopping too close to vehicles ahead. Moving into gaps that are too small. Looking for gaps that are larger than needed to perform maneuver. Following cars too closely. Hitting parked cars when parking. 3 to 4 second rule: For most vehicles, 3-4 seconds allows for a safe following distance when the road is dry and straight The 3-second rule is a simple way to double-check that you are driving at a safe following distance. Choose a fixed point that is even with the car in front of you, (such as a tree, a road sign or a mile marker). If you reach that same fixed point before you can count to three, then you are driving too close to the car in front of you and you need to fall back a bit. To compensate for problems with depth perception and judging how far away something is, a driver needs to use reference points and be able to change distance into time. Explain translating distance into time using the 3- to 4-second following distance rule. Explain that each second in that count translates into one car length. 3 to 4 second rule: For most vehicles, 3-4 seconds allows for a safe following distance when the road is dry and straight The 3-second rule is a simple way to double-check that you are driving at a safe following distance. Choose a fixed point that is even with the car in front of you, (such as a tree, a road sign or a mile marker). If you reach that same fixed point before you can count to three, then you are driving too close to the car in front of you and you need to fall back a bit
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Ways To Improve Vision Clean windows—inside and out
Clean vehicle’s outside lights and be sure they work Inspect wiper blades for damage and effectiveness Adjust mirrors properly Keep sunglasses and windshield scraper in vehicle Remove objects that interfere with vision
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Topic 3 Vehicle Referencing Points and Establishing Lane Position
Line of sight Targeting Blind Spots Lane Positions Vehicle Reference Points
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Line of Sight (LOS) Line-of-sight is the visible path of travel from your vehicle to the target area Your line of sight (LOS) is the visible path of travel from your vehicle to the target area, whether you are moving straight forward, turning, or backing up. A clear line of sight is needed for the brain to determine safe speed and steering adjustments. If your line of sight is obstructed, you need to slow down and prepare to brake or change position until your line of sight is clear. Line of sight can be affected by: The size and shape of the vehicle’s windows and interior; People, animals and cargo in the vehicle; Other vehicles, particularly large trucks; Bushes, trees, buildings; Hills, curves Weather conditions Can you think of any other factors that might affect line of sight? The more often you have to change lanes, brake, or otherwise maneuver your vehicle to reestablish a clear line of sight, the more risks you take for something to go wrong (e.g., for a car to rear-end you, to collide with another vehicle merging into the same lane as you). As a driver, your goal is to maintain an open line of sight to minimize the number of maneuvers you have to make. When something obstructs your LOS, you may need to adjust your speed and/or position until it is clear again
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Path-of-Travel (POT) Path-of-Travel is the series of continuous positions your vehicle will occupy while traveling toward your target area Path of travel is the series of continuous positions your vehicle takes in the process of moving to your target area. As a driver, you will determine your path of travel based on your target area, your line-of-sight, standard visual references, and the road environment between you and your target area. Theoretically, the most efficient way to get from point A to point B is a straight line; in reality, a variety of factors may necessitate that you alter the position of your car, breaking that straight line in order to safely reach your target. Question: What factors could require you to change your path of travel? Possible Answers: A vehicle that has broken down in the lane ahead; Road construction requiring lanes to merge or a detour; Potholes; etc. Some restrictions to path-of-travel are static, allowing drivers plenty of time to react and adjust their vehicles’ positions. However, it is critical for drivers to be alert to their surroundings and be prepared to react to sudden occurrences (e.g., a child darts out into the street after a ball; another vehicle runs a red light while you’re navigating the intersection; a deer bounds out of the woods) that alter their paths of travel with very little notice
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Identify the target in this driver’s path of travel
Selecting a Target Specific object Located straight ahead in the center of your path of travel Near visual field limit Steer towards Changes to whatever appears in the center of your path of travel Target New drivers tend to naturally gaze at the road immediately in front of the vehicle which is problematic because it distracts them from monitoring the road ahead and detecting traffic situations that may affect their paths of travel. To help new drivers avoid fixating on the road right in front of their vehicles, we use selecting a target to teach students how to consistently search the area around and between their vehicles and the targets. Selecting a specific target ahead allows the driver to adjust his/her speed and lane position Target: An object, (e.g., a car driving in front of you, a road sign, a tree, a building, etc.); Located straight ahead, in the center of your path of travel; Situated approximately seconds ahead of your vehicle or near the end of the center of your field of vision; That the driver steers the vehicle toward; The specific target object may change as you proceed along your path of travel As your field of vision changes, whatever appears in the center of your path of travel becomes the target. When driving through turns, curves, and/or hills, a target is at the end of the intended path of travel through the turn, curve or hill Drivers need to turn their heads to locate a new target when preparing for a turn or entering a curve Identify the target in this driver’s path of travel Do not stare at or fixate your gaze on the target itself…
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The Target Area Rather than focusing directly on the Target, continuously scan to the left and right of it (the Target Area) for relevant information and potential hazards. Did you see the sign? You don’t want to fixate on the target itself. The driving environment between you and the target may change at any moment. Continuously scanning the area to the left and right of the target (the target area), will allow you to see the big picture and give you time to identify and react to driving information and potential hazards. Searching the target area for driving-related information is more important than merely identifying a target The target area will tell you when there is a curve in the road, a hillcrest, traffic controls, work zones and other conditions that may need an adjustment in speed, lane position or communication Question: What other types of information and hazards should you be searching for in the target area? Possible Answers: Road signs (e.g., Stop, Yield, Children at Play, Lanes Merge Ahead), presence of pedestrians in cross-walks, vehicles pulling out into the road, etc. Advantages of using Targets and Target Areas to Develop Driving Skills Makes it easier to track lanes and keep your vehicle in a straight line, preventing weaving; When the driver looks far ahead of the vehicle, he or she will simultaneously gather information close to, and around the vehicle; Allows drivers to plan ahead better, anticipate necessary moves, and manage risks. For Example: When a driver sees a traffic light ahead turn from green to yellow he or she knows to begin decelerating and cover or provide pressure to the brake pedal depending on the distance between the vehicle and the stop line at the traffic light in order to prepare for the upcoming halt; Develops visual skills that are essential for preventing/detecting loss of traction; Improves drivers control of the steering wheel including how to correct for skids and how to prevent overcorrecting in the event that the driver momentarily loses control of the vehicle; Questions: If you look down at your feet as you walk down the hallway between classes… Can you walk in a straight line? Can you actively avoid bumping into other students, faculty and staff also navigating the hall? Can you identify when you need to turn into your next scheduled class? Can you read signs posted on the hallway walls that give vital information (e.g., Attention! Men’s and women’s lavatories in B Wing are closed due to flooding: Do Not Enter!”, or directional signs posted on your classroom door? (e.g., “Mr. Y’s class will be meeting in the science lab today,”)? Looking ahead does not prevent you from gathering information from the area immediately around you. For example, you do not have to be looking straight down at a set of stairs in order to walk up or down them without tripping. These skills are evidence of your brain gathering information from your eyes using Peripheral Vision, orienting yourself in space. Target Area
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Using Lane Position to Maximize Your Line of Sight
12 ft. Lane positions are based upon an average lane size of 12-feet wide, and a vehicle 6-feet wide This Diagram shows the three basic lane positions drives can use Select the lane position that gives you the best line of sight and safest path of travel 6 ft. 1 Since the lane is wider than your vehicle, you can position yourself within the lane in ways that communicate your intentions to other drivers, allows you more room in which to execute maneuvers, and create more space between you and potential hazards. The assumption is the vehicle is six feet wide and the lane is 12 feet wide, since standard traffic flow lanes are commonly 12 feet wide, and the average non-commercial vehicle is about 6 feet wide Drivers can position a vehicle in any of three different areas of their lane 2 3
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Standard Vehicle Reference Points for Lane Position 1
LEFT Reference Point 3 feet from pavement line or median Positioned in the center of lane with an equal buffer of space on either side. 3 feet from line or curb RIGHT Reference Point 3 feet from pavement line or curb Relates a part of the vehicle to some part of the roadway. Know your vehicle placement within a lane at all times. Maneuver in confined places.
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Standard Vehicle Reference Points for Lane Position 2
LEFT Reference Point: Vehicle is 3-6 inches from the pavement line or median. Preparing to make a left-hand turn. Determining position for parking on the left side of a one-way street. RIGHT Reference Point: Vehicle is 3-5 feet from curb, pavement line, or edge of road. Allows for additional space to the right of the vehicle. Used to prepare for a left turn or when avoiding a problem to the right of the vehicle. When in Lane Position 2, your left side reference point will appear when the pavement line or edge of the road line is visible, lining up about one foot in from the left edge of the hood Left Side Reference Points used for: Lane Position 2 Preparing for a left turn Determining position for parking on the left side of a one-way street (3-6 inches from the curb or line) When in Lane Position 2, your right side reference point will appear to line up with the middle of the right-half of the hood when you look at the curb, pavement line, or edge of the road. Right Side Reference Point used for:
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Standard Vehicle Reference Points for Lane Position 3
LEFT Reference Point: Vehicle is 3-5 feet from the pavement line or median RIGHT Reference Point: Vehicle is 3-6 inches from curb, pavement line, or edge of road Preparing to make a right-hand turn Determining position for parking on the right side of the street Allows for additional space to the left of the vehicle. Used to prepare for a right turn or when avoiding a problem to the left of the vehicle. Lane Position Three indicates that you might turn right and provides more space between your vehicle and hazards to your left. Lane Position Three Allows for 6 feet of space to the left of your vehicle (the driver side) and 3-6 inches to the right of your vehicle (passenger side) Use this position to Avoid a potential problem in the area (e.g., circumventing a pothole); Indicate to other drivers that you are preparing to turn right soon; Leave more room between your vehicle and hazards on your left When in Lane Position 3, your right side reference point will appear when the pavement line is visible, lining up just over the center of your vehicle’s hood.
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Possible Lane Positions
The width of the lane allows drivers to make lane position adjustments to minimize risk and create more space between their car and problem situations. LP 4 LP 2 LP 1 OBSTACLE LP 3 LP 5 Lane Positions – 1, 2, 3, 4, and 5
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Blind Spots of Pavement Around Your Vehicle
~16 feet ~9 feet ~16 feet ~48 feet ~6 ft. ~6 ft. The average American car is roughly a little over 16 feet long and 6 feet wide: that means, according to the figure in this slide, you are always surrounded by an irregularly shaped blind spot covering approximately 144 square feet where from the driver’s seat, you cannot see the area of pavement surrounded by your vehicle. The size of this area varies depending on the type of the vehicle and the driver’s height. Drivers can’t see the actual position of the car in relation to the roadway because the driver’s view of the road is blocked by the body of the car. From the driver’s seat you cannot see your vehicle’s bumpers or wheels, but you need to know where these parts of your vehicle are to properly position your vehicle within the lane you’re driving in, when stopping at intersections, and when parking. You can develop the ability to use objects outside of your vehicle that you can see as reference points to orient the vehicle to its spatial environment, such as using your hood ornament to gauge relation to the curb when parking. Areas the Driver Cannot See: Area of ground in front of the vehicle within approximately one car length (about 16 ft.) by one car’s width (about 6 ft.) Area of ground to the left (driver’s) side of the vehicle within approximately half of one car length (about 3 ft.) Area of ground to the right (passenger’s) side of the vehicle within approximately the width of one and a half cars (about 9 ft.) Area of ground behind the vehicle within approximately three car lengths back by one car width (about 6 ft.) Why are these areas blind? Because the necessary bulk of the vehicle made out of strong enough material to pass safety standards is very much opaque. The windows on the vehicle only permit the driver to see beyond the vehicle at a certain distance Student Activity: Have a student volunteer in the driver seat of a car while communicating with other members of the class where to place cones to identify the perimeter of the area of pavement that the driver cannot see. It should look approximately like the area occupied by the green cars in the slide. ~3 feet ~16 feet In the figure above, the green cars represent the size and areas of pavement that the driver of the white car cannot see.
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Standard Vehicle Reference Points for Front Limitation
1. 2. The driver should look out the right front window and allow the vehicle to creep forwards until the white line is directly under the passenger side mirror. 2. 1. As the vehicle approaches the white stop line, the driver will lose sight of the segment of line directly in front of the vehicle: so how does the driver know when to stop at the right place? Since you cannot see the front bumper of your vehicle from the driver seat, you must use front vehicle reference points to determine how close the front bumper of your car is to a stop line at an intersection or a curb in a parking lot. This reference point is especially useful when stopping at intersections and crosswalks, and when parking When you can look out the passenger side window and see the white stop line or the curb just underneath and running perpendicular to your passenger side-view mirror, you know that the nose of your bumper is directly above the beginning of the stop line or curb. 3. 3. This reference point will help you direct your vehicle to a stop, with the nose of the bumper positioned just over the beginning of the stop line.
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Standard Vehicle Reference Points for Rear
1. 2. 2. When you look back over your left shoulder, the curb should appear to intersect with the lower middle of the left rear window. 1. When you look back over your right shoulder, the curb should appear to intersect near the lower right side of the right rear window. You cannot see the rear bumper of your vehicle from the driver’s seat, so how can you tell where the rear end of your vehicle is when you’re backing up? When you look back over your right shoulder, the curb should appear to intersect near the lower right side of the right rear window of your vehicle (see figure 1.) When you look back over your left shoulder, the curb should appear to intersect with the lower middle of the left rear window of your vehicle (see figure 2); 3. 3. Using these reference points will allow you to back up to a curb, leaving an appropriate distance between it and your bumper.
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Topic 4 Basic Maneuvers – Steering and Braking
Holding the upper half of the wheel can result in excessive steering, air bag injuries, and upper body fatigue. Benefits to keeping your hands on lower half of the wheel: Puts the body in a natural position with relaxed shoulders. Promotes balanced control of the steering wheel, reducing excess motion. Improves stability by lowering the body’s center of gravity. Prevents arm injury if the airbag deploys. Most of the time, any sloppy method of using the steering wheel will "work;“ This leads to a driver getting positive feedback for a wrongful action, allowing the driver to become complacent and develop poor steering habits. Good steering habits are critical when a situation requiring quick-reaction time develops. While you may not experience such circumstances every time you drive, you can be sure that eventually, you will. And your body may react by defaulting to steering as you normally do—as you’ve trained it. If you remain calm and react with deliberate, measured reactions and good steering techniques, you can avoid losing control of your vehicle. Question: What type of sudden emergencies that require skillful steering could occur while driving? Answers: Tire blow-out Hydroplaning during rainy conditions Skidding on black ice Getting blown into another lane by a buffet of wind created by a large truck or bus passing you on an interstate Another vehicle cuts you off A deer jumps into the road Most modernly manufactured vehicles are equipped with power-steering and require much less effort on the part of the driver to change the direction of the vehicle. Benefits of using a lower grip on the steering wheel Puts the body in a natural position with relaxed shoulders Promotes balanced control of the steering wheel, reducing excess motion Improves stability by lowering the body’s center of gravity Prevents arm injury if the airbag deploys
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Hand-to-and/Push-Pull Steering
Hand-to-Hand Steering/Push-Pull To turn RIGHT: Left hand pushes up from 8 o’ clock to 11 o’ clock The first and most used steering technique is Push/Pull or hand-to-hand steering The steering technique is used for precision maneuvers, steering through curves, intersection entry and exit, and when front wheel (under steer) traction loss occurs This steering technique permits steering inputs ranging from minor (1-2 degrees) up to a half turn of the wheel, while keeping both hand on the wheel for precision adjustments Right hand pulls down from 1 o’ clock to 4 o’ clock
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Hand-Over-Hand Steering
Used at Speeds Below 15 mph Used for slow, tight turns - Arms cross on the top 1/3 of the wheel until desired path of travel is reached Left Turn/left hand Left hand pulls down, then reaches up to about the o’clock position and continues to pull down to the left Left Turn/right hand Right Hand pushes up to about the 11 o’clock position The second steering technique is called hand-over-hand and was most commonly used on older American vehicles equipped with center point steering assemblies. This technique is used when steering speed is critical, and at speeds below 15 mph When going slow more steering input may be necessary The most common situation would be pulling into a perpendicular parking position or turning into an alley with limited visibility to the path of travel Other situations may be a tight turn at a visually hidden intersection or possibly in rear-wheel skid (over steer traction loss) recovery This is true in forward as well as reverse maneuvers Begin hand-over-hand steering with a balanced hand position Unwind the wheel toward the path of travel using the same hand-over-hand technique on the right top third of the steering wheel, returning the hands to the neutral balanced position Keep hands on the wheel, do not let the steering wheel return without controlling the movement especially in front wheel drive vehicles Some wheels straighten out after a turn if the grip is relaxed, but many cars do not have this built into the rack and pinion steering apparatus or caster of the suspension Cautions: Using hand-over-hand steering as the primary steering method can be risky. This method may expose the driver to additional risk of injury to arms, hands, and/or face in the event of a crash that results in air bag inflation. As a primary steering technique, it also raises the risk of single vehicle off-road, roll-over crash occurrences. This is the primary fatal crash cause of the novice driver and instructors need to caution students on relying on this method as the primary steering. Steering inputs must be limited when in an off-road situation.
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One-Hand Steering Backing straight--hand holds top of wheel
The third steering technique is used when reaching away from the wheel to use a vehicle control or accessory; when backing in a straight line or parallel parking space; and backing out of a parking space. When driving forward, remove one hand from the wheel and keep the other hand at the balanced position on the right or left portion of the wheel Be aware of unintentional turning of the wheel when moving the hand to the top of the wheel while driving forward Wheel balance is difficult to maintain when crossing over the mid-plane of the body to the left or right—the human physiology allows more control when keeping one hand at the side of the wheel when driving forward Backing straight--hand holds top of wheel Backing a trailer--hand holds bottom of wheel
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Covering the Accelerator
Used for a smooth transition from braking to accelerating. Allows the vehicle to coast which may speed up or slow down the vehicle. Permits the driver to be prepared for any needed acceleration.
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Acceleration Techniques
Heel pivots foot from the brake pedal to the accelerator. Gently apply pressure to the accelerator pedal to gradually increase speed to minimize backward pitch and maintain vehicle balance. Progressive, Smooth Acceleration Typically used when passing or merging into higher speed traffic. Greater pressure is applied to accelerator pedal to rapidly increase speed without losing tire traction. Thrust Acceleration
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Smooth Braking Technique
Braking Techniques Position heel on floor in front of the brake to maximize braking controllability Ball of foot makes and maintains contact with pedals for smooth braking and accelerating Use the fine motor control forces of the ankle rather than gross motor control of the thigh muscles by using the ball of the foot to press the brake pedal Students who have difficulty reaching the pedals need to keep their heel down Some vehicle designs do not support pivoting the foot when brake pedal and accelerator pedals are not on the same plane—this uneven placement can cause the foot to hit the side of the pedal. Each vehicle usually has a different feel to the brake pedal pressure Apply too little pressure and the vehicle will not stop in the desired spot Apply too much pressure, the car balance may dip forward, the brakes may lock up, loss of traction and directional control can result Is a trait of a skilled driver. Saves gasoline, and wear and tear on the brake system and tires. Use ball of your foot to press pedal. Smooth Braking Technique
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Methods to Reduce Speed
1. Release the Accelerator Pedal Most frequently used method to slow vehicle speed. Gradually reduce pedal pressure to avoid abrupt changes in speed. Slowing the vehicle can first be accomplished by just releasing the accelerator pedal; sometimes you can just coast to a stop this way, only using the brake pedal at the end to maintain the standing position. Weight shifts to the front (forward pitch), resulting in reduction in speed This technique is more noticeable when the automatic transmission/transaxle is in a lower gear or in a standard transmission/transaxle vehicle This is why it is important to use a lower gear in an automatic transmission/transaxle in snow or icy conditions Abrupt release of accelerator pressure can and does increase the forward pitch forces, exposing the driver to unnecessary and dangerous risks
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Controlled Braking 2. Controlled Braking
Check the rearview mirror for vehicles coming up quickly behind you. Release accelerator and gradually apply smooth, steady pressure on the brake pedal. For a smooth stop, gently ease off the brake a few seconds before stopping to reduce the vehicle’s weight shift so the car does not pitch forward then backward during the final phase of stopping.
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Threshold Braking 3. Threshold Braking in an Emergency
Slows the vehicle as quickly as possible without locking brakes or losing traction. Release accelerator while checking for traffic behind you. Exert forceful pressure on the brake pedal; you will feel the vehicle’s weight shift forward. If you feel the wheels beginning to slide, ease off of the brake pedal so the tires can start rotating again.
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Trail Braking 4. Trail Braking Used for sharp turns.
Occurs at the transition point where you slightly reduce pressure on the brake pedal to allow the vehicle to begin to regain speed before applying the accelerator.
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Methods to Reduce Speed
1. Use controlled braking prior to reaching the curve 2. Begin easing off brake, and trail brake with very light pressure until halfway through the turn, 3. Accelerate out of the turn
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Speed Limit A speed limit is the maximum legal speed you can travel on a road under ideal conditions. You may drive slower than the posted speed, but it is illegal to drive any faster. By law, you must drive slower if conditions such as road construction or bad weather make the posted speed unsafe. It is illegal to use a radar detector in Virginia.
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Interstate highways in certain rural areas 70 mph
Maximum speed limit for passenger vehicles and motorcycles (unless posted otherwise) Type of Highway Zone Speed Limit Interstate highways in certain rural areas 70 mph Non-rural interstate highways, public roads not part of the interstate system 55 mph Rural rustic roads 35 mph School, business and residential zones (You are required to travel 25 mph in a school zone only when indicated by sign or signal. Otherwise maintain the posted speed.) 25 mph Note: Students need to know these speed limits for the learner’s permit knowledge test.
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Stopping Distance Three factors determine the distance that it takes to stop your vehicle: Perception time: The time it takes you to recognize a hazard. Reaction distance: The distance your vehicle travels between the time you recognize a problem and the time you apply the brakes. Braking distance: The distance your car travels after you apply the brakes. Perception time, reaction distance and braking distance are affected by weather, visibility, and your mental and physical condition. Braking distance is also affected by how fast your vehicle is traveling, the condition of your brakes and tires, and the pavement condition. For example, wet pavement can double your braking distance. We will go into greater depth about stopping distance later in this course. This is the information that you will need to know for the learner’s permit test.
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Average stopping distance on dry, level pavement
This information is on the DMV knowledge test… Source: Code of Virginia section
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Anti-Lock Braking System (ABS)
ABS allows maximum stopping force without locking up the brakes (skidding) If standard brakes are applied too hard, the wheels "lock" or skid, and you lose steering control. ABS is designed to maintain rolling traction and steering. Four-wheel anti-lock brakes are designed to prevent skidding and help drivers maintain steering control during an emergency stopping situation ABS can improve vehicle stability, steerability and stopping capability
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Stomp, Stay, Steer To get the most from ABS, remember STOMP, STAY and STEER. In an emergency: STOMP the brake pedal as hard as you can. The system's computer will prevent the tires from skidding by rapidly releasing and reapplying brakes at individual wheels. STAY on the pedal and continue pushing it as hard as you can. Finally, STEER where you want to go. To master this technique, you may want to practice using ABS before an emergency. Find an empty parking lot or similar safe area and give STOMP, STAY and STEER a try.
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Anti-Lock Braking System (cont)
If steering control is lost, the vehicle skids in a straight line wherever it is going ABS is an anti-lock/anti-skid brake system that allows the driver to steer during hard braking When a driver operating a four-wheel ABS equipped vehicle steps firmly on the brake pedal, the system automatically modulates the brake pressure at all four wheels, adjusting pressure to each wheel independently to prevent wheel lock-up
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Anti-Lock Braking System (cont.)
The ABS warning will come on when there is a problem with either the ABS brake system, normal brake system, or the brake fluid is low in the master cylinder or the ABS brake system To find out if a vehicle is equipped with ABS, turn on the ignition and check the instrument panel for the ABS indicator light Do practice driving with ABS. Find an empty parking lot or open area and practice emergency stops so that you can become accustomed to the feel - the normal pulsations - of ABS when it activates. • Do allow enough distance to stop. ABS doesn't necessarily allow you stop in a shorter distance; it primarily helps you to maintain directional control. Just because your car or truck is equipped with ABS doesn't mean you can take more chances. Do cars with ABS stop more quickly than cars without it? Not always. Although the stopping distance with ABS is shorter under most road conditions, drivers should always keep a safe following distance behind the vehicle ahead and maintain a speed consistent with the road conditions A vehicle with ABS maintains its steering capability during a sudden stop, but still will not turn as quickly on slippery roads as it would on dry pavement An ABS system pumps the brakes automatically, many times a second, to prevent lockup and help a driver to maintain control. On dry pavement, ABS doesn't substantially shorten stopping distances. But on wet or slippery surfaces, ABS can help a great deal - if a driver knows how to use it. Drivers are traditionally taught to pump the brakes on slippery roads to avoid a skid. But with ABS, firm and continuous pressure - not pumping - is required to activate the ABS feature.
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Practice Activating ABS
In a parking lot, go mph and execute an emergency stop to engage ABS Keep your foot firmly on the brake even when you feel the brake pulsate and/or hear noise This computerized pumping action can pump the brakes up to 15 times per second Never pump ABS brakes; doing so will only increase the stopping distance Can ABS stop all car skids? While ABS cannot prevent all skids, it does prevent the wheels from locking in typical panic situations ABS cannot, however, change natural laws of physics A combination of excessive speed, sharp turns and slamming on brakes can still throw an ABS-equipped vehicle into a sideways skid
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