Safe driving techniques

Chapter Objectives

• How to search the road ahead.
• How to manage vehicle operating space.
• How to gauge traction.
• How to apply natural laws to traction.
• How to drive smoothly to minimize weight shift when changing speed and direction

Vehicle Controls

• Vehicle speed and placement are controlled using the accelerator, brakes, and steering wheel.
• Smooth control use comes with practice, which allows drivers to "tune in" to the vehicle's feel and reaction to abrupt maneuvers.
• Smooth braking, accelerating, and steering rely on proper seat and steering wheel adjustment, along with correct foot positioning on the pedals.
• Driver's visual inputs are essential for vehicle control.
• Attention to driving and directed visual search influence crash risk.
• Look for objects or conditions within, along, or approaching the planned path of travel.
• Direct attention 20 to 30 seconds ahead and scan both sides to identify hazards.
• Knowing a vehicle's placement relative to objects helps determine the safety of moving into planned spaces.

Operating Space

• Adequate operating space is needed in all directions around a vehicle.
• Operating space acts as a "space cushion" for positioning the vehicle when needed.
• Space is a critical factor in reducing collision risks.
• As vehicle speed increases, the required operating space also increases, especially in front.
• Additional space provides more response time to hazards, weather, and traffic variations.
• Underestimating needed space can lead to accidents, ranging from minor to severe.
• Speed and position adjustments must align with operating space requirements.

Visual Control Zone

• Drivers should identify a visual control zone 12 to 15 seconds ahead as a planned path of travel for braking and steering corrections.
• An alternate path should be identified in case the visual control zone becomes blocked.
• A following interval of 3 to 4 seconds is advisable for adjusting speed or position.
• More than 3 to 4 seconds may be needed if the alternate path involves leaving the paved road.
• Drivers should stay alert to the size, lane position, speed and distance of vehicles behind them

Visual Referencing

• Visual reference points relate parts of the roadway to parts of the vehicle.
• These are used to manage space around the vehicle and maneuver precisely.
• Accurate space judgment depends on visualizing vehicle space, making references, understanding space needs, and honing driving skills.
• Driving experience and referencing are key for accurate space judgment.
• Each driver perceives roadway surface to vehicle positioning differently.
• Factors that influence drivers' perception include eye dominance, seat adjustment and height, head movement, and vehicle type.

Traction

• Traction is the adhesion between tires and the road surface.
• Without traction, steering, braking, or acceleration cannot occur leading to skidding.
• Traction relies on vehicle speed, tire condition, and roadway surface.
• Drivers control speed and tire condition, but must recognize road conditions that alter traction.

Road Surfaces

• Road surfaces vary in traction.
• The surfaces with most to least traction are concrete, asphalt, brick or polished concrete, dirt, gravel, and sand over hard surface.

Factors Affecting Traction

• Any substance on a road surface can reduce traction.
• Be alert for sewer covers, paint, vinyl strips, tar, wet leaves, sand, loose gravel, and mud.
• Substances have adverse effects on adhesion.
• Poor road conditions can lead to traction loss.
• Dirt and oil mixing with rainfall can make roads surprisingly slippery.
• Hydroplaning happens at speeds of 35 mph and a water depth of 1/12 inch, where tires ride on a water wedge.
• Speed, water depth, tire inflation, width, and tread affect hydroplaning speed.
• The onus is on the driver to prevent hydroplaning

Temperature & Design

• As temperature rises to 32°F from below freezing, icy, snow-packed areas become more slippery, especially at intersections.
• Roadway design can influence traction and control
• Crowned roadways are higher in the middle, while banked roadways are higher on one edge, usually at a curve.

Roadway Shoulders

• Roadway shoulders are off-road areas that provide an escape path.
• Shoulders have less traction than road surfaces.
• Be aware of shoulder conditions which may be rough, soft or covered in loose materials.
• Expect less traction when steering onto the shoulder.
• Unequal traction can cause skidding, particularly in vehicles without ABS
• Shoulders may not be level with the road surface, so be cautious if there is a difference in surface level.

Other Factors Affecting Traction

• Bridge surfaces, highway overpasses, and shaded areas may freeze before other road surfaces.
• Strong crosswinds can make steering difficult.
• Large buildings and embankments can block wind and cause shade and ice.
• Patches of ice and wet leaves can cause unequal traction.
• Moderate braking and accelerating can lead to traction loss and skidding.
• Natural laws such as inertia, gravity, and kinetic energy affect traction.

Inertia

• Inertia affects traction as an object in motion will continue to move straight ahead.
• Inertia can create problems when entering a turn at too high of a speed.
• Unless traction overcomes inertia, a car slides outside during turns.
• Inertia causes unsecured objects to move during deceleration or braking.
• Momentum is related to inertia and describes how much motion an object has based on its mass and velocity.
• Factors influencing the force of inertia when driving include sharpness of a turn, vehicle speed and size, roadway slope, and surface condition.

Gravity

• Gravity affects vehicle traction and performance.
• Its downward pull impacts a vehicle's ability to accelerate and maintain speed on hills.
• On a slippery uphill road, acceleration can result in loss of traction.
• Gravity boosts speed when driving downhill, which increases braking and stopping distances.
• Traction must overcome both gravity and inertia.

Kinetic Energy

• Movement requires energy, with faster objects needing more energy.
• Kinetic energy, is affected by vehicle weight and speed.
• Braking distance increases by the square of the speed increase.
• Crash impact force also increases by the square of the speed increase.

Vehicle Suspension

• Weight transfer is a shift of weight from one point to another, which occurs during acceleration, braking, or turning.
• Weight shift is influenced by acceleration, brake application, steering input, and surface traction.
• Weight can shift to the front, rear, sides, or corners.
• When stopped or moving at a constant speed, suspension and traction is stabilized.

Contact Patch

• Transferring weight changes a tire's contact patch, which is the amount of tire rubber in contact with the pavement.
• A larger contact patch results in more traction.
• The average tire's contact patch is about the size of an adult human palm.

Weight Transfer Points

• When a vehicle accelerates, weight shifts to the rear, compressing the rear suspension and increasing the rear tires' contact patch, while decreasing the front tires' contact patch.
• During aggressive acceleration, the front of the vehicle rises noticeably, and the rear drops.
• When a vehicle decelerates, weight shifts to the front.
• With hard braking, the front of the vehicle drops noticeably, and the rear rises.
• Occupants feel forward movement.
• If too little brake pressure is applied, the vehicle may not stop at the desired point.
• When turning, a vehicle's weight shifts in the opposite direction.
• When turning right, weight shifts left causing the vehicle to lean left.
• The degree of weight shift depends on speed, traction, and steering input.

Maximizing Traction

• To maximize traction and minimize weight shift and possible traction loss, avoid sudden inputs when accelerating, braking, and steering.
• Braking sharply during a turn quickly can lead to a skid.
• Focusing on one input at a time (brake, then steer, then accelerate) can maintain maximum vehicle stability and traction.
• Drivers should sit in an upright position behind the steering wheel to control vehicle balance and maximize the view of the driving environment.