CDL General Knowledge practice test

Below 40 mph, leave at least one second for every 10 feet of vehicle length. 40 feet means 4 seconds.

Above 40 mph, add one second to the one-second-per-10-feet rule. 4 seconds plus 1 equals 5.

Total stopping distance is the distance you travel while you see the hazard, react to it and brake to a stop.

The average alert driver takes about 3/4 of a second to react after seeing and recognizing a hazard.

Braking distance grows with the square of speed. Double the speed and it takes roughly four times the distance to stop.

Brakes, tires, springs and shock absorbers work best when loaded. An empty truck can lock wheels and skid more easily.

With enough water on the road, tires can lose contact with the surface at speeds as low as 30 mph.

Looking 12 to 15 seconds ahead gives you time to spot hazards and change speed or lanes. At highway speed that is about a quarter mile.

On a two-lane road, place one device within 10 feet of the vehicle on the traffic side, one about 100 feet behind and one about 100 feet ahead.

Traffic only approaches from behind on a divided or one-way road, so all three devices go behind: at 10, 100 and 200 feet.

If a hill, curve or other obstruction blocks the view, move the rear device back as far as 500 feet so drivers get enough warning.

Front (steering) tires need at least 4/32 inch of tread in every major groove. Other tires need at least 2/32 inch.

More than 10 degrees of play, roughly 2 inches of movement at the rim of a 20-inch wheel, makes the vehicle hard to steer.

A leaf spring with one-fourth or more of its leaves missing puts the vehicle out of service.

Most serious skids come from going too fast for road conditions. Over-braking, over-steering and over-accelerating also cause skids.

To regain traction, let the rear wheels roll again: stop braking, ease off the accelerator, then steer where you want to go and be ready to countersteer.

Top-heavy trucks need a lot of distance to stop. A quick turn often avoids the hazard in less space.

Hard braking on a soft shoulder can cause a skid. Slow down gradually and keep one side on the pavement if possible.

When you reach 5 mph over your safe speed, brake firmly until you are 5 mph under it, then release. Repeat as needed.

Shifting down on a steep grade can be hard or impossible. Pick the right low gear before you start down.

Federal law sets the limit for commercial drivers at 0.04% blood alcohol concentration, half the usual limit for car drivers.

Class C is for electrical fires. Class B is for flammable liquids like gasoline and grease. Most trucks carry a B:C extinguisher.

The cooling system is under pressure when hot. Opening it can spray scalding coolant. Let the engine cool first.

You need at least one tiedown per 10 feet of cargo and never fewer than two, no matter how small the load.

Check cargo within the first 50 miles, then every 3 hours or 150 miles, whichever comes first, and after every break.

Convex mirrors show a wider area but make things look smaller and farther away. Keep that in mind when judging distance.

Dim your lights within 500 feet of an oncoming vehicle and when following another vehicle so you don't blind the driver.

Pick a gear that gets you all the way across before you start. Shifting on the tracks can stall the vehicle.

Swinging left before a right turn invites cars to pass you on the right. Keep the back of the trailer near the curb so no one can squeeze in.

Backing toward the driver's side lets you watch the rear of the vehicle by looking out the window. Use a helper whenever you can.

Class A covers combinations with a gross combination weight rating of 26,001+ lbs where the towed unit is over 10,000 lbs.

Class B covers heavy single vehicles (26,001+ lbs GVWR) that tow 10,000 lbs or less.

Class C covers smaller vehicles that carry 16+ people (counting the driver) or placarded hazardous materials.

Federal rules require you to hold the commercial learner's permit for at least 14 days before taking the skills test.

A CLP holder must be accompanied by a qualified CDL holder of the right class seated in the front seat beside them.

You can get a CDL at 18 in most states for driving within the state, but interstate driving requires you to be at least 21.

Medical examiner's certificates last up to 2 years. Some conditions require shorter periods.

Two serious violations within 3 years means at least 60 days of disqualification. Three means at least 120 days.

A first offense for driving under the influence means at least a 1-year disqualification, or 3 years if you were hauling placarded hazmat.

Any detectable amount of alcohol, even below 0.04%, puts a CMV driver out of service for 24 hours.

Report any traffic conviction in any vehicle, except parking, to your employer within 30 days.

You must notify your employer before the end of the business day after you receive notice of a suspension, revocation or disqualification.

Having more than one license is illegal. A court may fine you and you must return extra licenses.

Trucks must carry a fire extinguisher, spare electrical fuses (unless they use circuit breakers) and three reflective warning triangles.

Recapped and regrooved tires are not allowed on the front wheels of a bus.

Rust streaks around lug nuts are a sign the nuts may be loose. Check them before driving.

Broken or leaking exhaust parts can let carbon monoxide into the cab or sleeper berth.

Two hands on opposite sides gives you the most control if you hit a curb or pothole.

Retarders can cause the drive wheels to skid on slippery roads. Turn them off when the road is wet, icy or snowy.

Getting out to look (GOAL: Get Out And Look) is the best way to see what's behind you. Back slowly and use a helper if you can.

Using the outer (right-hand) left-turn lane gives you room to swing wide without cutting off the other lane.

Starting too early can make the trailer cut the corner and hit cars waiting to turn.

Signaling someone to pass is risky because they may not have a clear road. You could be held responsible if they crash.

At night, keep your speed low enough to stop within the area lit by your headlights.

Braking in a curve can lock the wheels or cause a skid. Slow down before you enter it.

Lowboys, car carriers and similar units can hang up on raised crossings. Don't cross if you might get stuck.

Trains can't stop quickly. A freight train can need a mile or more to stop, so never try to beat one across.

Federal rules ban texting and holding a mobile phone while driving a CMV. Fines are steep and you can be disqualified.

Only sleep cures fatigue. Coffee and fresh air don't fix it.

The body needs time to get rid of alcohol. Nothing else speeds it up.

Heat raises tire pressure and temperature. Check tires every 2 hours or 100 miles in hot weather.

Light braking while moving slowly creates heat that dries the brakes.

Black ice is a thin, clear layer. If ice is forming on your mirrors or antenna, the road may be icy too.

When ice forms on parts of your truck, the road surface is likely icing too.

High beams reflect off fog and make it harder to see. Slow down and use low beams.

Get off the road in an open area. Never pull into a service station.

Stay upwind so smoke and flames blow away from you.

First protect the scene, using flashers and triangles, then notify authorities and care for the injured.

Moving an injured person can make injuries worse. Only move them if staying puts them in danger.

Drivers must inspect cargo and know it is properly secured, even when others loaded it.

Gross vehicle weight rating is the maximum loaded weight the manufacturer specifies for a single vehicle.

Heavy cargo stacked high raises the center of gravity and makes rollovers more likely, especially on curves.

A strong header board keeps cargo from moving forward into the cab in a sudden stop.

You can't inspect sealed loads, but you're still responsible for staying within gross weight and axle limits.

Blocking is shaped to fit snugly against cargo and is secured to the deck so the cargo can't shift.

Covers keep cargo from blowing or spilling onto the road and shield it from weather.

Any vehicle required to have hazmat placards needs a driver with the H endorsement.

Turn on flashers immediately when you stop, then put out warning devices within 10 minutes.

Set out warning devices as soon as possible and within 10 minutes of stopping.

Work zones have narrow lanes, sudden stops and workers close to traffic. Slow down and stay alert.

Don't make eye contact or challenge them. Let them go and report dangerous driving if you can do it safely.

Check mirrors often, and before changing lanes, turning or merging, to track traffic and watch your load.

Check mirrors more than once and signal early, since vehicles can move into your blind spots.

Large trucks have big blind spots behind and on the right side, plus close in front and beside the cab.

With double clutching you press the clutch, shift to neutral, release, match engine speed, press again and shift into the next gear.

Drifting is a warning sign of fatigue. Get off the road and rest.

Use low beams when following so you don't blind the driver ahead through their mirrors.

Winter checks include coolant and antifreeze, defrosters, wipers, washer fluid, tires and chains.

Escape ramps stop runaway vehicles safely. Use one if you lose your brakes; it's better than crashing.

Check securement within the first 50 miles and every 3 hours or 150 miles, and after breaks.

Engine braking does most of the work. Short, firm brake applications (snub braking) keep the brakes from overheating.

Hot brakes lose their stopping power. Using the right low gear on grades prevents fade.

ABS keeps the wheels from locking. Brake normally and firmly; don't pump the pedal.

After a crash, spilled fuel, flat tires, wiring shorts, fuel leaks and flammable cargo are common causes of fires.

Watch for drivers who drift, change speed oddly or make jerky moves. Give them plenty of room.

Begin by approaching the vehicle and looking for damage, fluid leaks, leaning and anything around it that's in the way.

Cuts deep enough to show the ply or belt, bulges, and leaks make a tire unsafe.

Radial and bias-ply tires must not be used together on the same axle.

Steering right avoids a head-on crash and keeps you off the oncoming lane. Most of the time it's the safest escape.

Looking well ahead gives you time to slow down or change lanes smoothly instead of reacting at the last second.

More space in front lets you slow down gradually, so the tailgater is less likely to hit you.