MN CDL General Knowledge flashcards

34 cards. Read the term and the definition here. The deck at the top of this page is optional.

Pre-trip inspection purpose

The pre-trip inspection confirms the vehicle is safe to operate before driving. It covers the engine compartment, lights, tires, brakes, coupling devices, and emergency equipment, and defects must be reported in writing.

Air brake leak test limits

With a fully charged system and engine off, leakage must be 3 psi per minute or less for a single vehicle and 4 psi per minute or less for a combination. With brakes applied, limits are 4 and 6 psi per minute.

Low-air warning threshold

The low-air warning buzzer and light must activate before pressure falls below 60 psi, and the spring brakes must apply automatically between 20 and 45 psi.

Steering axle tread minimum

Steering axle tires must have at least 4/32 inch tread depth. All other tires need at least 2/32 inch. Recapped or regrooved tires are not allowed on the steering axle.

Double-clutching procedure

Accelerate to governed rpm, push in the clutch, shift to neutral, release the clutch briefly, push it in again, select the next gear, and release smoothly. This matches engine and transmission speeds.

Backing with a helper

Before backing, get out and check behind the vehicle. Keep the helper visible in the mirrors. If the helper disappears from view, stop immediately until communication is restored.

Trailer off-tracking

The rear wheels of a long combination vehicle cut inside the path of the front wheels during a turn. Drivers must allow extra room for the trailer to clear curbs, poles, and pedestrians.

Right turn technique

Swing wide enough to clear the inside curb but not so wide that you enter another lane. Watch the trailer's rear wheels off-tracking toward the curb and check both mirrors throughout the turn.

Signaling distance

Signal at least 100 feet before a turn in business or residential areas and at least 200 feet on highways. Signal early so other drivers can react before you change direction.

Four-way flashers use

Use four-way flashers when stopped on a shoulder, moving slowly below 40 mph on a highway, or driving a vehicle that is a hazard to others. Turn them off before normal driving.

Scanning ahead

Look 12-15 seconds ahead in city traffic and 20-25 seconds ahead on the highway. This lets you spot brake lights, merging traffic, and road hazards before they become emergencies.

Distraction threshold

Taking your eyes off the road, hands off the wheel, or mind off driving for more than 2 seconds sharply increases crash risk. At 55 mph, 2 seconds covers about 160 feet.

Following distance rule

Allow at least one second per 10 feet of vehicle length at speeds under 40 mph, and add one second over 40 mph. A 60-foot vehicle at 55 mph needs about 7 seconds.

Total stopping distance

Total stopping distance equals perception distance plus reaction distance plus brake lag distance plus braking distance. Perception-reaction alone takes about 1.75 seconds, covering 142 feet at 55 mph.

Air brake lag

Air brakes take about 0.4 seconds to engage after the pedal is pressed, covering roughly 32 feet at 55 mph. This lag adds to total stopping distance compared with hydraulic brakes.

Speed in special zones

School zones, business districts, and residential areas typically have a 25 mph limit unless posted otherwise. Posted limits apply to ideal conditions; reduce speed for rain, snow, ice, and curves.

Tire blowout response

Hold the wheel firmly, do not brake hard, and ease off the accelerator. Let the vehicle slow gradually, then pull off the road. Hard braking after a blowout can cause a loss of control.

Stuck accelerator response

Shift to neutral, brake firmly, and pull off the road. Do not turn off the engine while moving, because you would lose power steering and power brakes.

Brake failure response

Downshift to use engine braking, pump the brakes if the system is air or hydraulic, apply the parking brake gradually, and steer toward an escape route such as a runaway ramp.

Rear-wheel skid recovery

Release the brake or accelerator and steer in the direction you want the front of the vehicle to go. Look where you want to go, not where the vehicle is sliding, and avoid sudden corrections.

Front-wheel skid recovery

The vehicle will not respond to steering. Ease off the accelerator and brake gently to regain traction, then steer smoothly once the front tires grip again.

Black ice locations

Black ice forms first on bridges, overpasses, and shaded areas. Treat these surfaces as slippery even when the road looks dry, and reduce speed before reaching them.

ABS braking technique

With anti-lock brakes, apply firm steady pressure and steer. Do not pump the brakes. ABS prevents wheel lockup and helps maintain steering control during hard braking.

Federal axle weight limits

Single axles are limited to 20,000 lb, tandem axle groups to 34,000 lb, and gross vehicle weight to 80,000 lb without a permit. The bridge formula may further limit axle group weights.

Cargo tiedown rule

Use at least one tiedown per 10 feet of cargo length, with a minimum of two for any load over 5 feet. The combined working load limit must be at least 50% of the cargo weight.

Rear overhang marking

Cargo extending more than 4 feet behind the rear of the vehicle must be marked with a red flag in daylight or a red light at night to warn following drivers.

Slack adjuster check

Check pushrod travel on each brake chamber; excessive travel means the brakes are out of adjustment. Typical limit is about 1 inch for a type 30 chamber, per manufacturer specification.

Oil pressure warning

If the oil pressure warning light comes on, stop the engine immediately and check the oil level. Continuing to drive with low oil pressure can destroy the engine.

11-hour driving limit

Property-carrying drivers may drive no more than 11 hours after 10 consecutive hours off duty, and must stay within a 14-hour on-duty window. A 30-minute break is required after 8 driving hours.

34-hour restart

After 34 consecutive hours off duty, the 60-hour/7-day or 70-hour/8-day cycle resets. This allows drivers to begin a fresh work cycle without carrying prior hours forward.

Train stopping distance

A freight train traveling 55 mph needs a mile or more to stop. Trains cannot swerve, so drivers must never try to beat a train at a crossing.

Stall on railroad tracks

Get everyone out and move at least 100 feet away from the tracks, then call 911 and the railroad emergency number. Do not stay in the vehicle trying to restart it.

CDL alcohol limit

Commercial drivers are prohibited from driving with a blood alcohol concentration of 0.04% or higher, half the 0.08% limit for non-commercial drivers. Refusal to test brings at least a one-year disqualification.

School bus stop rule

Stop for a school bus with flashing red lights and an extended stop arm unless you are on a divided highway with a median separating you from the bus.