Chapter 3

Weight distribution

Vehicle's weight can be shifted from the center of the chassis, with the weight distributed approximately equally over the front and rear tires, to a position where weight is concentrated over the front, rear, left or right tires.

Steering Position

Drivers should sit in a comfortable, upright position directly behind the steering wheel

Planned path of travel

a planned path of travel, 12 to 15 seconds ahead. Under most conditions a following interval of three or four seconds will enable you to adjust speed or position appropriately

Visual Referencing

a visual reference point relates some part of the road way to some part of the vehicle.

Substances on the road

any substance on a road surface can reduce traction. Such as sewer covers, paint, vinyl strips, tar, wet leaves, sand, loose gravel or mud.

Traction

is the adhesion, friction or grip between the tires and the road surface. Without it, a driver cannot steer, brake, or accelerate. A loss of it may result in skidding.

Single Vehicle Crashes

more than 50% of occupant fatalities occur as a result of single vehicle crashes. Crashes involve improper steering or braking or a combination of the two.

What do you control

the speed and placement of the vehicle

Roadway Shoulders

they provide the only escape path in an emergency. Provides less traction than the road surface.

Maximizing traction

to maximize traction and minimize the chance of traction loss, avoid sudden inputs when accelerating, braking or steering. For example, applying the brakes when cornering too fast will slow the vehicle very little, and may cause a skid because of severe weight shift. Also, focus on executing one input at a time-brake, then steer, then accelerate

Changing Vehicle suspension load-front to rear

when a vehicle accelerates, its weight shifts to the rear

Gravity and a hill

when going up a hill, you myst accelerate to keep a constant speed and overcome the force of gravity. On a slippery hill acceleration may result in a loss of traction.

Driving down hill

when you drive down a hill, the force of gravity tends to boost speed, which increases the stopping distance.

Surface Materials from greatest to the least of traction

1. concrete 2. asphalt 3. brick or polished concrete 4. dirt 5. gravel 6. sand over hard surface

Five factors influence the effect of Inertia

1. sharpness of the turn or curve 2. speed 3. size, height, weight and load of the vehicle 4. roadway slope 5. roadway surface condition

A matter of balance

A transfer of weight from one point of the vehicle to another occurs whenever the driver accelerates, brakes, turns or performs some combination of these actions

Temperature Change

As temperatures rise from below freezing to about 32 degrees, icy and snow-packed areas become more slippery. Wet ice is much more slippery than dry ice.

Kinetic Energy

Movement requires energy, and the faster an object moves, the more energy is needed. Is affected by the vehicle's weight and speed.

Surface Conditions

Poor road conditions such as rippled surfaces or potholes can contribute to a loss of traction. Be alert when the road is wet, it may cause hydroplaning.

Traction Varies with the Vehicle's....

Speed, tire condition and roadway surface

Conditions that can affect traction

Surface materials Substances on the road Surface conditions Roadway design

Inertia

Traction also is affect by inertia. An object in motion continues to move straight ahead until acted upon by some outside force. This force creates problems when a driver changes a vehicle's direction too suddenly. As the car travels around the corner, inertia tends to keep the car moving forward tin a straight line, rather than allowing the car to follow the curve or turn.

Changing Vehicle suspension load-rear to front

When the brakes are applied, the vehicle's weight or center of mass is transferred to the front

Changing Vehicle suspension load-side to side

When turing, a vehicle's weight will shift in the direction opposite the turn. When turning right, the vehicle will shift to the left

Operating Space

you will need adequate operating space in front of, to the sides of, and to the rear of your vehicle.