CDL General Knowledge Test Concept Review

Overview

This chapter covers why commercial drivers inspect their vehicles, what defects to look for, and how to do an inspection the same way every time. Federal and state laws require drivers to inspect their vehicles, and inspectors can put an unsafe vehicle out of service until it is fixed.

There are three kinds of inspection. The pre-trip inspection finds problems before you leave. During the trip, you watch your gauges, use your senses, and check critical items such as tires, brakes, lights, trailer connections, and cargo securement whenever you stop. The after-trip inspection and report tell the motor carrier what needs repair.

The defects to know are specific. Front tires need at least 4/32 inch of tread in every major groove and other tires at least 2/32 inch. Steering wheel play of more than 10 degrees makes steering hard. Rust around wheel nuts may mean they are loose. You must also carry spare fuses (unless the vehicle has circuit breakers), three red reflective triangles, and a charged fire extinguisher.

Overview

This chapter covers the basic skills for moving a heavy vehicle under control: starting smoothly, steering firmly, stopping smoothly, backing safely, and shifting gears. These skills matter more in a large vehicle because mistakes take longer to correct.

When you start on a hill with a manual transmission, partly engage the clutch before you take your foot off the brake so you do not roll back. Hold the wheel firmly with both hands on opposite sides. Backing is always dangerous, so avoid it when you can. When you must back, do it slowly in the lowest reverse gear, toward the driver's side, and with a helper when possible.

Most heavy manual transmissions need double clutching. Downshift before you start down a hill and before you enter a curve. A retarder helps slow the vehicle and saves the brakes, but it can make the drive wheels skid, so turn it off on wet, icy, or snowy roads.

Overview

This chapter covers how to see what is happening around a large vehicle and how to let other road users know what you are doing. Not looking properly is a major cause of crashes, and other drivers may not notice even a big truck in plain sight.

Look 12 to 15 seconds ahead, which is about one block in town and about a quarter mile on the highway, and shift your eyes between near and far. Check your mirrors often, and more often during lane changes, turns, merges, and tight moves. Convex mirrors show a wider view, but they make things look smaller and farther away than they are.

Signal early and keep signaling until the turn is done. Flash your brake lights to warn drivers behind you when you will slow down, and do not wave other drivers by. When you stop on a road or shoulder, turn on your flashers and put out warning devices within 10 minutes. On a two-way road, place them within 10 feet of the front or rear corner, 100 feet behind, and 100 feet ahead. On a one-way or divided highway, place them 10, 100, and 200 feet back toward traffic.

Overview

This chapter covers how speed and space keep a large vehicle out of trouble. Driving too fast is a major cause of fatal crashes, and heavy vehicles need much more room to stop and turn than cars do.

Total stopping distance is perception distance plus reaction distance plus braking distance. When you double your speed, braking distance becomes about four times longer. Wet roads can double stopping distance, so cut your speed by about one-third on a wet road and by half or more on packed snow. If you hydroplane, release the accelerator and push in the clutch, and do not brake. Empty trucks can take longer to stop because they have less traction.

Keep at least one second of following distance for every 10 feet of vehicle length below 40 mph, and add one more second above 40 mph. If someone tailgates you, add space in front and slow down gradually. Watch the space overhead, since an empty van sits higher than a loaded one. On right turns, keep the rear near the curb and turn wide at the end, and with two left-turn lanes, use the outside one.

Overview

This chapter covers seeing hazards before they become emergencies, and staying fit and focused enough to react to them. A hazard is any road condition or road user that could become a danger, such as a driver drifting toward an exit, a stopped delivery truck, or children playing near the road.

Move-over laws ask you to slow down and, when safe, change to a lane not next to an emergency vehicle or work zone on the roadside. Distracted drivers drift and change speed, so give them room. If an aggressive driver confronts you, get out of their way, avoid eye contact, and do not respond to gestures. Federal rules ban texting and hand-held phone use while driving a commercial vehicle, except to contact police or emergency services.

It is illegal to drive a commercial vehicle with a blood alcohol concentration of 0.04% or more, and any detectable alcohol below that puts you out of service for 24 hours. Only time sobers a person up. Fatigue is just as dangerous: when you are drowsy, the only real cure is to get off the road and sleep, and a short nap does more than a coffee stop.

Overview

This chapter covers driving when you cannot see well or when weather makes the vehicle and road act differently: at night, in fog, in winter, and in very hot weather. In each case you need to slow down and check your vehicle more carefully.

At night, people see less sharply and are blinded by glare. Low beams let you see only about 250 feet ahead, so drive slowly enough to stop within your headlight range. Dim your lights within 500 feet of an oncoming vehicle or one you are following. In fog, the best choice is to pull off and wait. If you must drive, slow down before you enter it, use low beams and fog lights, and avoid passing.

In winter, check coolant, defrosters, wipers, tires, and chains, and watch for black ice, which makes the road look only wet. Bridges freeze before the road. After deep water, keep light pressure on the brakes to dry them. In very hot weather, check tires every 2 hours or 100 miles, never let air out of hot tires, and never remove the radiator cap until the system has cooled.

Overview

This chapter covers two places where a heavy vehicle has little room for error: railroad-highway crossings and long, steep grades. At a crossing, a train cannot stop for you. On a downgrade, gravity keeps pushing your speed up.

Approach every crossing expecting a train. Passive crossings have only signs and markings, so the decision is yours. Active crossings have flashing lights, bells, or gates. Do not race a train, do not rely only on signals, and do not shift gears on the tracks. A typical tractor-trailer needs at least 14 seconds to clear a single track and more than 15 seconds for a double track. If you get stuck, get out and away from the tracks, then call the emergency number posted at the crossing or 911.

Before a long downgrade, choose a safe speed for your weight, the grade, the road, and the weather, and shift to a low gear before you start down. Engine braking is your main speed control. Too much braking makes brakes fade from heat. Use the proper method: when you reach your safe speed, brake until you are about 5 mph below it, release, and repeat. Know where the escape ramps are.

Overview

This chapter covers what to do when something goes wrong suddenly: another vehicle in your path, a brake or tire failure, a skid, a crash, or a fire. Good habits help prevent emergencies, but when one happens, your chances depend on how well you act.

You can usually turn to miss an obstacle faster than you can stop. Keep both hands on the wheel, do not brake while turning, and be ready to countersteer. If an oncoming driver drifts into your lane, a move to the right is usually best. For emergency stops, use controlled braking or stab braking instead of jamming on the brakes. If a tire blows, hold the wheel firmly and stay off the brake until you slow down.

ABS keeps wheels from locking so you can steer, but it does not always shorten stopping distance. Most skids come from driving too fast for conditions. At a crash, protect the area, notify authorities, and care for the injured. For a fire, pull off in an open area, keep van doors closed for a cargo fire, and aim the extinguisher at the base of the fire from upwind.

Overview

This chapter covers the driver's duty to haul cargo safely, even when someone else loaded it. Loose or poorly balanced cargo can fall off, shift in a quick stop, overload the vehicle, or make it hard to steer.

Check the cargo during your pre-trip inspection, again within the first 50 miles, and then every 3 hours or 150 miles and after every break. Know the weight terms: gross vehicle weight is what the vehicle and load actually weigh, and the rating is the maximum the manufacturer allows. Keep the load low with the heaviest items under the lightest, and balance it so the steering and drive axles each carry enough weight.

Use blocking, bracing, and tiedowns to stop cargo from moving. Use at least one tiedown for each 10 feet of cargo and never fewer than two. Cover open loads to protect people from spills and the cargo from weather. You cannot inspect a sealed load, but you must still make sure you are within gross and axle weight limits.

Overview

This chapter covers what every commercial driver must know about hazardous materials, even without the hazardous materials endorsement. Hazardous materials are products that pose a risk to health, safety, and property during transport, such as explosives, gases, flammable liquids, poisons, and corrosives.

The rules exist to contain the product, communicate the risk, and ensure safe drivers and equipment. Shippers describe the materials on shipping papers and put diamond-shaped labels on packages. Drivers must keep hazardous materials shipping papers where responders can find them: in a pouch on the driver's door, in clear view within reach while driving, or on the driver's seat when out of the vehicle.

Placards are diamond-shaped signs on the outside of the vehicle. A placarded vehicle needs at least four identical placards, on the front, rear, and both sides. If a vehicle requires placards, you may drive it only with the hazardous materials endorsement. Four-digit identification numbers, shown after UN or NA, help first responders identify the material.