Chapter 4 DEFENSIVE DRIVING

Transcription

1 Chapter 4 DEFENSIVE DRIVING

2 Chapter 4 Table of Contents Chapter 4 DEFENSIVE DRIVING DEFENSIVE DRIVING Positioning The Bus When Making a Turn at an Intersection Making the perfect turn Professional Drivers Use All the Space Available to Them (Space that is designated and / or Yielded to them) When necessary to make turn into wrong lane The hazards of crossing into the wrong lane on the approach street A turn from the wrong lane and into the wrong lane Over Tracking Increased Wheel base - Increased Over Tracking and the Length of Side Swipe Line Over Tracking - The relationship of the rear wheels to the front wheels when turning Over Tracking Overhang Increased Overhang - Increased Swing Out. Smaller Radius (Tighter Turn), Increase Swing Out. Increase Speed - Larger Radius (Wider Turn) The hazards of the overhang Vehicle Dynamics Natural Laws Perceptive Driving Hydroplaning Obstructing an Intersection Backing Safely

3 DEFENSIVE DRIVING Positioning The Bus When Making a Turn at an Intersection 1. Activate Turn Signal. 2. Check Mirror. 3. Stop Short of Intersection. 4. Keep Wheels Straight While Stopped. 5. Check Traffic and Mirrors Again. 6. Proceed at Slow Speed. 7. Make Sure Other Drivers Have Yielded Before Invading Their Space. Making the perfect turn 1. When approaching a right turn, position the bus in the left portion of your lane. 2. While making the turn, use your right mirror to keep the right rear wheels as close to the apex of the turn as possible, without striking the apex. 3. The perfect turn is completed when the vehicle has stayed in the proper lane throughout the turn. NOTE: The apex of a turn is the center of the turn or the point the two sides of an angle meet. Professional Drivers Use All the Space Available to Them (Space that is designated and / or Yielded to them) 1. When a driver fails to use all the space available to them, the results can be as shown in the drawing at the right. 4-3

4 When necessary to make turn into wrong lane 1. Use the wrong lane of the road that you are entering, instead of the road you are leaving. 2. It is easier to see any approaching vehicles that might be in the lane you are turning into. 3. If you can get their attention so they can yield to you or give them the right of way. The hazards of crossing into the wrong lane on the approach street 1. Vehicles from behind may try to pass on the right. 2. Vehicles approaching from the opposite direction may not yield. 3. Vehicles turning from an intersection onto the approach street may not see the bus. A turn from the wrong lane and into the wrong lane 1. In the real world, we have turns that violate all the principles of safe driving. 2. Think safety!! These turns have to be made using extreme caution. 3. Make sure the traffic is cleared or has yielded the right of way to your vehicle. NOTE: Whenever these conditions arise, the bus driver has to do the best that they can in handling the problem. ** If an accident should happen while making a turn like this, the driver could be charged with the accident. 4-4

5 Over Tracking Increased Wheel base - Increased Over Tracking and the Length of Side Swipe Line The Side Swipe Line - The part of the vehicle between the front and rear axles. 1. This is the Portion of the vehicle that tends to go to the inside of the curve when a vehicle turns. 2. The amount that will go to the inside depends on the length of the line from axle to axle. 3. Therefore if the wheel base is increased the side swipe line is increased. Over Tracking - The relationship of the rear wheels to the front wheels when turning. 1. When turning, the rear wheels tend to go to the inside of the front wheels. 2. The longer the wheel base, the more the rear wheels will tend to go to the inside. 3. A slower speed will allow the vehicle to turn sharper, therefore causing the rear wheels to over track more. Over Tracking 1) The relationship of the rear wheels to the front wheels when turning. a) The rear wheels do not follow the front wheels in a turn. b) The rear wheels will tend to go to the inside of the front wheels. c) The longer the wheel base of the vehicle, the more the rear wheels will go to the inside. 2) The vehicle should be positioned so the rear wheels will pivot around the apex. a) Turns should be squared off when making a turn in a large vehicle. b) The wheels should not be turned until the vehicle is further into the intersection than is normal with a car. c) The turn should be made at a slower speed to facilitate a sharper turn. 3) If enough room is not allowed for the rear wheels, they may strike the curb or ditch in a right turn, or another vehicle in a left turn. 4-5

6 Overhang Increased Overhang - Increased Swing Out. Smaller Radius (Tighter Turn), Increase Swing Out. Increase Speed - Larger Radius (Wider Turn) Overhang - The portion of the bus that extends from the rear axle to the bumper. 1. When turning, the rear end will swing out in a direction opposite the turn. 2. The amount of the swing out is in direct relation to the amount of overhang on the vehicle. 3. The greater the overhang on the vehicle, the more the swing out. 4. The tighter the turn and slower the vehicle is moving, the greater the amount the rear end will swing out. NOTE: This could be as much as 18 to 20 inches, depending on the amount of overhang. The hazards of the overhang 1. If the bus is too close to the center line or lane line the bus is turning from, the rear of the bus may cross over the line, putting the rear of the bus in the wrong lane. 2. This is a hazard if another vehicle is passing or meeting the bus in the other lane. 4-6

7 Vehicle Dynamics Natural Laws When we think of laws, we think about those enacted by legislative bodies. These are man-made laws. In the case of motor vehicles, these laws are a part of an examination we must take and pass to earn the right to drive. These laws place certain limitations on our driving. But there are other laws that place even greater limitations on our driving capability. These laws are not published, few are included in driver tests and if they are overlooked, they can create hazards and even impair our ability to a point that makes it unsafe for us to drive. These are the Laws of Nature. I. VEHICLE DYNAMICS A. Velocity 1. Speed of vehicle. 2. All moving objects have kinetic energy (energy in motion) and the object will continue to move until the energy is used up or converted. Energy cannot be destroyed, it must be converted. It is converted to friction and heat by applying brakes. 3. Never Forget - The amount of kinetic energy depends on the velocity or speed of the vehicle. 4. Kinetic energy does not develop in direct proportion to speed. a) 2 = 4? When you double your speed, the kinetic energy is multiplied four times. EXAMPLE: At 20 MPH you can stop a vehicle in 60 ft., but at 40 MPH it will take 240 ft. to stop (See accompanying chart). THIS IS A NATURAL LAW YOU CAN CONTROL. B. Centrifugal Force 1. This force tends to keep an object in motion moving in a straight line. a) In driving a motor vehicle this force is encountered when going around curves when curve goes to the left, your body sways to the right. 2. Why is this so critical? 3. It tends to overcome both friction and gravity, so speed is the controlling factor. THIS IS ANOTHER NATURAL LAW YOU CAN CONTROL. C. Inertia 1. The property of matter to remain motionless or moving in a straight line unless acted upon by an outside force. a) Friction (through the brakes and/or tires) is one way to control inertia. b) Striking another object will stop inertia. D. Friction 1. Resistance to relative motion between two bodies in contact. 2. Friction is the Dr. Jekyll and Mr. Hyde in motor vehicles. a) To the engine, drive train, and other closely mated moving parts, friction is a killer. 4-7

8 (1) These parts must be checked in order to keep them properly lubricated, so friction will be kept at its lowest point. 3. Friction is absolutely necessary to a vehicle in motion. a) We could not go around a curve, up a hill, stop or even start without friction. b) Approximately 40 sq. in. per tire is all that lies between you and the road, so good brakes and tires are essential to stopping the vehicle. c) Road surface is another consideration in friction. Hard surface roads offer more friction than dirt and gravel, dry better than wet and a wet surface is better than snow and ice covered. E. Gravity 1. This is the force that tends to pull an object toward the center of the earth. a) Gravity is most apparent when going up or down a hill. b) When going uphill gravity has a retarding effect and power must overcome this force. c) When going downhill gravity creates an accelerating effect and brakes or some form of retardation must be applied to keep vehicle under control. F. Braking 1. Artificial force applied to stop movement. a) This is one element of control that requires two frictional applications. b) Friction between the tires and road and friction between the brake shoe or pad and brake drum or disc. 2. In this process, friction creates heat in both tires and brakes. a) When smoke boils around skidding tires, this is heat. (1) The farther a tire skids, more heat is dissipated and there will be less stopping power. b) Heat builds up in heavy braking - for instance on long down grade - causing brakes to fade or even catch on fire. G. Tracking 1. The position of rear tires in relation to the front tires when turning. 2. The longer the wheel base, the greater a danger of rear tires over tracking. a) The rear wheels will not follow in the same tracks as the front wheels when a vehicle turns. b) The sharper the turn and a longer wheel base will have a large affect on the amount of over tracking. H. Force of Impact 1. To overcome kinetic energy, we must use it up. a) If we use the brakes to convert energy to friction and heat, we can stop the vehicle safely. b) However, if we use energy up by striking another object, that is another thing. 2. Force of impact is dependent upon three factors. a) Weight of vehicle. b) Speed of vehicle. c) Distance in which it was stopped. The laws of nature can be a friend to us or a real enemy. We must be aware of these laws and be able to control their forces. These laws are always with us and we need to watch for one key element SPEED an element that turns the natural laws into a most deadly enemy. 4-8

9 Perceptive Driving I. S I P D E A. Search B. Identify C. Predict D. Decide E. Execute II. How to use S I P D E A. Search - Scanning and observing with eyes. 1. Look for road and traffic hazards. B. Identify - Mind 1. Real and potential hazards. 2. Critical objects and conditions in traffic. C. Predict - Mind 1. How these objects and conditions might produce a hazard. D. Decide Mind 1. Action that will minimize risk of collision. E. Execute - Muscle 1. Action that will be effective in avoiding hazard. 2. Separate a) Changing vehicle speed in order to avoid dealing with two or more real hazards at the same time. Allow the hazards to separate. 3. Comprise a) Choosing a path of travel and speed that will give the least risk of damage when multiple hazards do occur. 4. Isolate a) Maintaining an adequate space or cushion on all sides by adjusting speed. 5. Stabilize a) Maintaining a constant lane position and speed. 4-9

10 The chart above shows the stopping distances of passenger cars and school buses. The chart is broken down into different speeds for both vehicles with the reaction distance at the top of the bar and actual braking distance at the bottom of the bar. The reaction distance is proportional to the speed of the vehicle. This is based on a reaction time of 3/4 of a second, which is a typical reaction for most drivers under most driving conditions. However, the braking distance is disproportional to the increase of the speed of the vehicle. This means that when the speed is doubled, as is the case of the reaction time, the braking distance will not be doubled. The actual braking distance will increase about four times. 4-10

11 Hydroplaning Hydroplaning, due to water on the road and loss of traction, can only be combated by a reduction of speed. In the event of hydroplaning, steering in the direction of the skid may be necessary. Following distance, visibility, weight, tires, road conditions, residue on the pavement, etc., all contribute to the severity of this condition. Obstructing an Intersection No driver shall enter an intersection unless there is sufficient space on the other side of the intersection to accommodate the vehicle he is operating without obstructing the passage of other vehicles or pedestrians, notwithstanding any traffic control signal indication to proceed. Backing Safely Due to the length and blind spots on a school bus, turns and backing create the largest percent of accidents. Changing lanes, cutting corners, and backing into streets to turn around all require close concentration. Do not allow distractions to lessen your ability to see and know where all obstacles are, especially during a backing maneuver. Because you cannot see everything behind your vehicle, backing is always dangerous. Avoid backing whenever you can. When you park, try to park so you will be able to pull forward when you leave. When you have to back, here are a few simple safety rules: Always turn on your hazard lights. Look at your path. Back slowly. Use an adult helper whenever possible. Never back into a main street. Avoid backing across lanes of traffic if possible. Never back on a school campus without the use of a spotter. Placing stops at a turnaround is not recommended. However, drivers may have some of these stops assigned on their routes. Should this occur, the following procedures will be followed: 1. Students should be loaded before backing. 2. After loading students, the driver should then execute the backing maneuver in a cul-de-sac or intersecting street. Avoid using personal driveways as a turnaround as the weight of the bus can do considerable damage. 3. When unloading students, the driver should execute the turnaround maneuver before letting any student off the bus. 4. The same steps should be taken in executing the turnaround as were mentioned in loading students at a turnaround stop. 4-11

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