Oklahoma CDL General Knowledge key terms

The full distance a vehicle travels before it stops, made up of perception distance, reaction distance, brake lag, and actual braking distance. It grows quickly as speed rises and on slippery surfaces.

The distance traveled while your eyes see a hazard but your brain has not yet recognized it as a danger. It depends on speed and how alert and attentive the driver is.

The distance covered between recognizing a hazard and actually applying the brake or taking other evasive action. Fatigue, distraction, and alcohol lengthen it noticeably.

The short delay in an air brake system between pressing the treadle and the brakes actually applying, because air must travel through lines and valves. It is roughly a fraction of a second and adds distance at speed.

Stopping distance increases with the square of speed, so doubling speed roughly quadruples braking distance. This is why a few extra miles per hour matter greatly in heavy vehicles.

The gap you keep behind the vehicle ahead, measured in seconds rather than feet. One second per ten feet of vehicle length at speeds under 40 mph, and more at higher speeds or poor conditions.

The safety margin of open space kept around all sides of your vehicle so you have room to stop or steer away from trouble. It includes front, rear, and side room.

A planned path or open space you identify in advance so you have somewhere to steer if traffic ahead suddenly stops or a hazard appears. Always keep at least one in mind.

The skill of scanning ahead and spotting potential problems early, such as brake lights, merging traffic, or pedestrians near the curb. Early detection buys time to react smoothly.

Continuously looking far ahead, to the sides, and in mirrors instead of staring at the vehicle in front. It helps you spot changing conditions and plan lane position and speed.

Regularly checking both flat and convex mirrors to know what is beside and behind you, especially before changing lanes, turning, or backing. Convex mirrors show more area but make objects look smaller and farther away.

The area beside or behind the vehicle that cannot be seen in the mirrors. Large vehicles have big blind spots, so you must turn your head or use mirrors carefully before moving over.

The safe sequence for moving to another lane: check mirrors, signal early, check the blind spot, and move only when the lane is clear and your speed matches traffic. Signal your intent well ahead.

A systematic check of the vehicle before driving, covering tires, brakes, lights, fluids, coupling devices, and cargo securement. It is required and helps catch defects that could cause a crash or breakdown.

The physical loop around the vehicle during a pre-trip inspection, checking each item by sight and touch. You look for leaks, damage, loose parts, and proper lighting from every side.

Checking tires for proper inflation, tread depth, cuts, bulges, and matching sizes. Bad or mismatched tires can cause blowouts, poor traction, and loss of control, especially on steering axles.

A check that the brakes hold the vehicle and work properly, such as a static air-loss or applied-pressure test and a low-speed stopping test. It confirms the system is safe before you drive.

A braking system that uses compressed air to apply the brakes instead of hydraulic fluid. It includes a compressor, tanks, valves, and spring brakes, and requires understanding of pressure and warning signals.

Emergency and parking brakes that are held applied by strong springs and released by air pressure. If air pressure drops too low, they apply automatically and bring the vehicle to a stop.

A light and buzzer that alert you when air pressure falls below a safe level, typically around 60 psi. If it comes on, stop safely because spring brakes may soon apply on their own.

A check that the compressor raises pressure to a safe operating range within a reasonable time while the engine runs. Slow buildup can signal a leak or a weak compressor.

The foot-operated valve a driver presses to apply the air brakes. How hard and how far you press controls how much air pressure reaches the brake chambers.

A tractor pulling one or more trailers, joined by a coupling system. It is longer, heavier, and less maneuverable than a single unit, so turns, stops, and lane changes need extra planning.

The horseshoe-shaped plate on the tractor that locks onto the trailer kingpin. A proper lock is confirmed by a tug test and by checking the release handle is in place.

The sturdy vertical pin under the trailer that locks into the tractor's fifth wheel. It is the main connection point transferring trailer weight and pulling force to the tractor.

After coupling, you gently pull forward with the trailer brakes set to confirm the fifth wheel has locked onto the kingpin. If the tractor moves without resistance, the coupling is not secure.

A heavy hook-and-latch coupling used to tow trailers with a lunette eye, common on straight trucks and some doubles. Always check the latch is closed and secured before driving.

The tendency of the rear wheels of a long vehicle to follow a path inside the front wheels during a turn. It means you must swing wide and watch the trailer's rear in tight spaces.

The wide arc a long vehicle's front end takes when turning right, which can strike nearby objects or vehicles. You must turn wide enough to clear hazards while keeping the trailer's rear from hitting the curb.

Tying down and containing a load with straps, chains, binders, or walls so it cannot shift, fall, or blow off. Federal rules set minimum numbers of tiedowns and working load limits.

The maximum load a tiedown or securement device is designed to hold safely, usually a fraction of its breaking strength. Sum the limits of your tiedowns against the cargo weight.

The combined working load limits of all tiedowns used on a load. Rules require the total to equal at least half the weight of the cargo being secured.

Movement of cargo during driving, which can change weight distribution, damage the vehicle, or cause a rollover or loss of control. Proper blocking, bracing, and tiedowns prevent it.

How a load's weight is spread across axles so no axle is overloaded and steering and braking stay effective. Load heavy items low and centered, and check axle limits.

What to do if a tire fails at speed: hold the wheel firmly, keep the vehicle straight, ease off the accelerator, and avoid hard braking. Then slow gradually and pull off the road safely.

The technique for regaining control when wheels lose traction: stop braking, ease off the accelerator, and steer in the direction you want the front of the vehicle to go. Avoid sudden inputs.

When water on the road lifts the tires off the surface so they lose contact and traction. It causes sudden loss of steering and braking, so slow down in heavy rain.

A diamond-shaped warning sign placed on vehicles carrying regulated hazardous materials, showing the hazard class. Placards warn emergency responders and the public what danger is present.

One of nine categories that group hazardous materials by their main danger, such as flammable, corrosive, or radioactive. The class determines placarding, packaging, and handling rules.

Written guidance carried with hazardous cargo, such as shipping papers and emergency response guides, telling responders and the driver what to do in a spill or fire. Keep it within reach.

Changing transmission gears to match engine speed and road speed, using the clutch and throttle smoothly in a manual vehicle. Proper shifting avoids lugging, over-revving, and loss of control on grades.

A shifting method for non-synchronized manual transmissions: press the clutch, shift to neutral, release the clutch, then press it again to engage the next gear. It matches gear speeds and reduces wear.

Choosing a low enough gear before a downgrade so engine braking helps control speed, instead of relying only on the brakes. Shift down before the hill, not while descending.

Loss of braking power caused by overheating, often from riding the brakes down a long grade. Using a lower gear and controlled braking helps prevent it.