MI CDL General Knowledge key terms

The total distance a vehicle travels from the moment the driver perceives a hazard until the vehicle comes to a complete stop, combining perception distance, reaction distance, and braking distance.

The distance traveled while the driver's eyes and brain recognize that a hazard exists, before any physical response begins; typically about one second of travel at highway speed.

The distance covered between recognizing a hazard and actually pressing the brake pedal, roughly three-quarters of a second to one second for an alert driver.

The distance a vehicle travels from the moment the brakes are applied until it stops; it grows with the square of speed, so doubling speed roughly quadruples braking distance.

The buffer of empty space kept around the vehicle on all sides so the driver has room to steer or brake if traffic ahead changes suddenly.

The gap in seconds between your vehicle and the one ahead; at least one second per ten feet of vehicle length, plus one extra second at speeds above 40 mph.

Following another vehicle too closely, which removes the time and space needed to stop if that vehicle brakes suddenly; a common cause of rear-end collisions.

The area alongside and behind a vehicle that cannot be seen in the mirrors; a driver must check it by turning the head before changing lanes.

Moving from one traffic lane to another; requires signaling, checking mirrors and blind spots, and confirming there is enough space before moving over smoothly.

The light used to announce an intended turn or lane change; signal early and cancel afterward so other drivers are not misled about your intentions.

A systematic walk-around check of the vehicle before driving, covering tires, lights, brakes, fluid leaks, coupling devices, and cargo securement, documented as required.

The end-of-day check of the vehicle for defects and required items, recorded in the driver's report so problems can be repaired before the next trip.

The written or electronic record a driver completes listing any defects found during inspection; the carrier must repair them and certify the repairs before the vehicle is used again.

A sequence of checks on the air brake system, including static leak tests and a check that the low-pressure warning and emergency spring brakes activate properly, performed before driving.

The engine-driven pump that builds and maintains air pressure in the brake system; the governor cuts it in and out to keep pressure within the operating range.

A valve that senses system air pressure and controls the compressor, cutting it in when pressure falls and out when the reservoirs reach the set maximum.

A warning light and buzzer that activate when air pressure drops below a safe level, typically around 60 psi, alerting the driver to stop before braking is lost.

Brakes held open by air pressure and applied by heavy springs when pressure is lost, automatically stopping the vehicle if the system fails.

A mechanical brake, often spring-applied in air brake systems, used to hold a parked vehicle in place; must be set before leaving the cab.

The loss of braking power caused by overheating of brake drums or shoes after repeated or prolonged use, common on long downgrades; controlled by gearing down instead of riding the brakes.

Using the engine's compression resistance, usually by downshifting, to slow the vehicle and spare the service brakes on long or steep downgrades.

An escape lane of deep gravel or sand built into a steep grade to stop a vehicle that has lost braking ability; steer into it rather than continuing downhill.

Changing to a lower gear, which reduces speed and increases engine braking; must be done at the correct speed to avoid over-revving or damaging the transmission.

Changing to a higher gear as speed increases; in a heavy vehicle this is normally done without the clutch using engine speed matching.

A shifting technique for non-synchronized transmissions: clutch in, shift to neutral, clutch out, match engine speed, clutch in again, and engage the next gear.

Shifting a non-synchronized transmission without using the clutch by matching engine and road speed; requires skill and is not permitted in every jurisdiction.

Loss of traction in which the tires slide instead of rolling; corrected by releasing the brake or accelerator and steering in the direction you want the vehicle to go.

A condition in which tires ride on a layer of water and lose contact with the road, causing loss of steering and braking; reduce speed in heavy rain to prevent it.

The tendency of the rear wheels of a long vehicle to follow a path inside the front wheels when turning, so the driver must swing wide and watch the mirrors.

A turn that in a large vehicle often requires swinging left first and checking the right mirror to keep the trailer clear of the curb and pedestrians.

The use of tiedowns, straps, chains, and blocking to keep cargo from shifting or falling; the number and strength of tiedowns depend on cargo weight and length.

Placing cargo so weight is balanced and within axle and gross weight limits, with heavier items low and centered to preserve steering and braking stability.

Carrying more weight than the vehicle's axles, tires, or gross weight rating allow; it reduces control, increases stopping distance, and can lead to fines.

Federal rules limiting driving and on-duty time and requiring rest periods, designed to prevent fatigue-related crashes; limits vary by property-carrying and passenger-carrying operations.

An electronic system that automatically records driving time and duty status, replacing paper logs for most drivers and helping enforce hours-of-service limits.

Physical and mental tiredness that slows reaction time and judgment; managed by adequate sleep, scheduled breaks, and stopping to rest when drowsiness appears.

The body's internal clock that creates natural drowsy periods, especially in the early morning and mid-afternoon, when crash risk from fatigue is highest.

The percentage of alcohol in the bloodstream, used as the legal measure of intoxication; commercial drivers are held to a lower limit than other drivers.

Alcohol or drug testing required when a supervisor has specific, articulable observations suggesting a driver is under the influence, such as slurred speech or erratic behavior.

The legal principle that by driving a commercial vehicle a person agrees to submit to alcohol and drug testing; refusing can result in license suspension and disqualification.