CDL Practice Tests: Driving Safely

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Question #46 (1 of 10)

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How much tread depth is required on all tires except steer tires?

  • 9/32 of an inch
  • 4/32 of an inch
  • 2/32 of an inch
  • 7/32 of an inch

Tire Problems

  • Too much or too little air pressure.
  • Bad wear. You need at least 4/32-inch tread depth in every major groove on front tires. You need 2/32 inch on other tires. No fabric should show through the tread or sidewall.
  • Cuts or other damage. Tread separation.
  • Dual tires that come in contact with each other or parts of the vehicle.
  • Mismatched sizes.
  • Radial and bias-ply tires used together.
  • Cut or cracked valve stems.
  • Re-grooved, recapped, or retreaded tires on the front wheels are prohibited.
You may have to know this for the test, and you will have to know this for doing your job. You need 4/32 of an inch of tread depth on the steer tires and 2/32 of an inch on all other tires.
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Question #183 (2 of 10)

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What determines blood alcohol concentration?

  • The amount of alcohol you drink, how fast you drink, and your weight
  • The amount of alcohol you drink, your gender, and the amount time since you last had a drink
  • The amount of alcohol you consume, your weight, and your tolerance to alcohol
  • How fast you drink and your weight

What Determines Blood Alcohol Concentration. BAC is determined by the amount of alcohol you drink (more alcohol means higher BAC), how fast you drink (faster drinking means higher BAC) and your weight (a small person does not have to drink as much to reach the same BAC).

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Question #50 (3 of 10)

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Which of the following describes what you're checking for when inspecting truck tires?

  • Properly inflated, slightly different size dual tires on trailer, maximum 4/32 tread depth
  • Properly inflated, valve stems and caps OK, no serious cuts, bulges, tread wear, tires not rubbing each other and nothing stuck between them
  • Properly inflated, steer tires must be recaps or retreads, dual trailer tires must be a combination of bias ply and radial, no rust streaks
  • Properly inflated, only slight peeling of retread cap allowed, minimum 3/4 inch tread depth
Condition of tires — properly inflated, valve stems and caps OK, no serious cuts, bulges, tread wear, tires not rubbing each other and nothing stuck between them.
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Question #87 (4 of 10)

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Wet roads can increase stopping distance by how much?

  • 30%
  • Double
  • Quadruple
  • 10%

Slippery Surfaces. It will take longer to stop and be harder to turn without skidding when the road is slippery. Wet roads can double your stopping distance. You must drive slower to stop in the same distance as on a dry road. Reduce speed by about one-third (e.g., slow from 55 to about 35 mph) on a wet road. On packed snow, reduce speed by half or more. If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so.

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Question #122 (5 of 10)

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What must you check for when inspecting tire chains?

  • Check the chains for broken hooks, worn or broken cross-links, and bent or broken side chains
  • All these are correct
  • Make sure the chains will fit your drive tires
  • Carry the right number of chains and extra cross-links.

Tire Chains. You may find yourself in conditions where you cannot drive without chains, even to get to a place of safety. Carry the right number of chains and extra cross-links. Make sure they will fit your drive tires. Check the chains for broken hooks, worn or broken cross-links, and bent or broken side chains. Learn how to put the chains on before you need to do it in snow and ice.

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Question #60 (6 of 10)

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Special conditions where you should downshift are:

  • Before entering a curve and before starting downhill
  • Before starting downhill or before slick spots on the road
  • After you've come to a complete stop or after you've entered a curve
  • Before entering a curve and after leaving a traffic light

Special conditions where you should downshift are:

  • Before Starting Down a Hill. Slow down and shift down to a speed that you can control without using the brakes hard. Otherwise the brakes can overheat and lose their braking power. Downshift before starting down the hill. Make sure you are in a low enough gear, usually lower than the gear required to climb the same hill.
  • Before Entering a Curve. Slow down to a safe speed and downshift to the right gear before entering the curve. This lets you use some power through the curve to help the vehicle be more stable while turning. It also allows you to speed up as soon as you are out of the curve.
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Question #65 (7 of 10)

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Many large vehicles have curved (convex, “fisheye,” “spot,” “bugeye”) mirrors that show a wider area than flat mirrors. This is often helpful, but be aware that:

  • These mirrors are useless during a turn
  • Everything seems larger and closer than it really is
  • Objects will be skewed toward the outside edges of the mirror
  • Everything seems smaller and farther away than it is
Many large vehicles have curved (convex, “fisheye,” “spot,” “bugeye”) mirrors that show a wider area than flat mirrors. This is often helpful, but be aware that everything appears smaller in a convex mirror than it would if you were looking at it directly. Things also seem farther away than they really are. It is important to realize this and to allow for it.
Fisheye mirrors are great, but they take some getting used to.
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Question #93 (8 of 10)

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Which of the following is a sign of standing water on the road?

  • Raindrops
  • All of these are signs of standing water on the road
  • Tire splashes
  • Clear reflections
Road surfaces where water can collect can create conditions that cause a vehicle to hydroplane. Watch for clear reflections, tire splashes, and raindrops on the road. These are indications of standing water.
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Question #47 (9 of 10)

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Why should you do a vehicle inspection the same way each time?

  • So you will learn all the steps and be less likely to forget something.
  • It's required by law
  • Every driver does inspections the same way
  • There is really only one way to do them
You should do a vehicle inspection the same way each time, so you will learn all the steps and be less likely to forget something.
It's much faster, easier, and more thorough to do the inspection the same way each time. Once you're taught the method for doing inspections, stick with it.
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Question #198 (10 of 10)

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Identification numbers are:

  • An eight-digit code used by border-crossing agents to identify hazardous materials and will be preceded by the letters "ND" or "AD."
  • A six-digit code used by dispatchers to identify hazardous materials and will be preceded by the letters "NA" or "UN."
  • A four-digit code used by first responders to identify hazardous materials and will be preceded by the letters "NA" or "UN."
  • A two-digit code used by first responders to identify hazardous materials and will be preceded by the letters "ND" or "AD."

Identification Numbers. Identification numbers are a four-digit code used by first responders to identify hazardous materials. An identification number may be used to identify more than one chemical on shipping papers. The identification number will be preceded by the letters “NA” or “UN.” The US DOT Emergency Response Guidebook (ERG) lists the chemicals and the identification numbers assigned to them.

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About The Safe Driving CDL Exam

The Safe Driving portion of the CDL manual will be on the General Knowledge portion of the CDL permit written exam. This is a rather large section of the CDL Manual and also includes basic information on hazardous materials (HazMat) that all drivers should know. Here are the basics of what you must know:

  • Vehicle Inspection
  • Basic Control of Your Vehicle
  • Shifting Gears
  • Seeing
  • Communicating
  • Space Management
  • Controlling Your Speed
  • Seeing Hazards
  • Distracted Driving
  • Aggressive Drivers/Road Rage
  • Night Driving
  • Driving in Fog
  • Winter Driving
  • Hot Weather Driving
  • Railroad-highway Crossings
  • Mountain Driving
  • Driving Emergencies
  • Antilock Braking Systems
  • Skid Control and Recovery
  • Accident Procedures
  • Fires
  • Alcohol, Other Drugs and Driving
  • Staying Alert and Fit to Drive
  • Hazardous Materials Rules

Vehicle Inspections

Safety is the most important reason for completing a vehicle inspection. A vehicle defect found during an inspection could prevent problems later, such as a breakdown on the road that will cost time and dollars, or even worse, a crash caused by the defect.

Federal and state laws require that drivers inspect their vehicles. Federal and state inspectors also may inspect your vehicles. If they judge the vehicle to be unsafe, they will put the vehicle "out of service" until it is repaired.

Generally speaking the major things you'll be checking will be:

  • Tire Problems
  • Wheel And Rim Problems
  • Break Drums And Shoes
  • Steering System Defects
  • Suspension System Defects
  • Exhaust System Defects
  • Safety Equipment Present
  • Cargo Properly Loaded And Secured

Pre-Trip Inspection

In order to obtain a CDL, you will be required to pass a pre-trip vehicle inspection test. You will be tested to see if you know whether your vehicle is safe to drive. You will be asked to do a pre-trip inspection of your vehicle and explain to the examiner what you would inspect and why.

The pre-trip inspection is a long, exhaustive inspection and we're not going to cover it all here. But we do have an excellent pre-trip inspection in our forum, done by one of our moderators who is currently a trainer at Prime Inc.

Daniel's Pre-Trip Inspection

Questions You Should Be Able To Answer

Here are some questions you should be able to answer before taking your CDL permit exam:

  • 1. What is the most important reason for doing a vehicle inspection?
  • 2. What things should you check during a trip?
  • 3. Name some key steering system parts.
  • 4. Name some suspension system defects.
  • 5. What three kinds of emergency equipment must you have?
  • 6. What is the minimum tread depth for front tires?
  • 7. Name some things you should check on the front of your vehicle during the walk-around inspection.
  • 8. What should wheel bearing seals be checked for?
  • 9. How many red reflective triangles should you carry?
  • 10. How do you test hydraulic brakes for leaks?
  • 11. Why put the starter switch key in your pocket during the pre-trip inspection?

Basic Control Of Your Vehicle

To drive a vehicle safely, you must be able to control its speed and direction. Safe operation of a commercial vehicle requires skill in:

  • Accelerating - Speed up smoothly and gradually so the vehicle does not jerk. Rough acceleration can cause mechanical damage. When pulling a trailer, rough acceleration can damage the coupling.
  • Steering - Hold the steering wheel firmly with both hands. Your hands should be on opposite sides of the wheel. If you hit a curb or a pothole (chuckhole), the wheel could pull away from your hands unless you have a firm hold.
  • Stopping - Push the brake pedal down gradually. The amount of brake pressure you need to stop the vehicle will depend on the speed of the vehicle and how quickly you need to stop. Control the pressure so the vehicle comes to a smooth, safe stop. If you have a manual transmission, push the clutch in when the engine is close to idle.
  • Backing safely - Because you cannot see everything behind your vehicle, backing is always dangerous. Avoid backing whenever you can. When you park, try to park so you will be able to pull forward when you leave.

Backing Safely

When you have to backup, here are some simple safety rules:

  • Start in the Proper Position - Put the vehicle in the best position to allow you to back safely. This position will depend on the type of backing to be done.
  • Look at Your Path - Look at your line of travel before you begin. Get out and walk around the vehicle. Check your clearance to the sides and overhead, in and near the path your vehicle will take.
  • Use Mirrors on Both Sides - Check the outside mirrors on both sides frequently. Get out of the vehicle and check your path if you are unsure.
  • Back Slowly - Always back as slowly as possible. Use the lowest reverse gear so you can more easily correct any steering errors. You also can stop quickly if necessary.
  • Back and Turn Toward the Driver's Side - Back to the driver's side so you can see better. Backing toward the right side is very dangerous because you cannot see as well. If you back and turn toward the driver's side, you can watch the rear of your vehicle by looking out the side window.
  • Use driver-side backing - even if it means going around the block to put your vehicle in this position. The added safety is worth it.
  • Use a Helper - Use a helper when you can. There are blind spots you cannot see, so a helper is important. The helper should stand near the back of your vehicle where you can see the helper. Before you begin backing, work out a set of hand signals that you both understand. Agree on a signal for "stop."

Shifting Gears

There are a couple of special conditions where you should downshift:

Before Starting Down a Hill - Slow down and shift down to a speed that you can control without using the brakes hard. Otherwise the brakes can overheat and lose their braking power. Downshift before starting down the hill. Make sure you are in a low enough gear, usually lower than the gear required to climb the same hill.

Before Entering a Curve - Slow down to a safe speed and downshift to the right gear before entering the curve. This lets you use some power through the curve to help the vehicle be more stable while turning. It also allows you to speed up as soon as you are out of the curve.

More Questions You Should Be Able To Answer

  • 1. Why should you back toward the driver's side?
  • 2. If stopped on a hill, how can you start moving without rolling back?
  • 3. When backing, why is it important to use a helper?
  • 4. What's the most important hand signal that you and the helper should agree on?
  • 5. What are the two special conditions where you should downshift?
  • 6. When should you downshift automatic transmissions?
  • 7. Retarders keep you from skidding when the road is slippery. True or False?
  • 8. What are the two ways to know when to shift?

Stopping Distance

This is very important to know and may be asked about on your CDL exams:

Total Stopping Distance = Perception Distance + Reaction Distance + Braking Distance

Perception distance - The distance your vehicle travels, in ideal conditions, from the time your eyes see a hazard until your brain recognizes it. Keep in mind, certain mental and physical conditions can affect your perception distance. It can be affected greatly depending on visibility and the hazard itself. The average perception time for an alert driver is 1 3/4 seconds. At 55 mph, this accounts for 142 feet traveled.

Reaction distance - The distance you will continue to travel, in ideal conditions; before you physically hit the brakes in response to a hazard seen ahead. The average driver has a reaction time of 3/4 second to one second. At 55 mph this accounts for 61 feet traveled.

Braking distance - The distance your vehicle will travel, in ideal conditions; while you are braking. At 55 mph on dry pavement with good brakes, it can take about 216 feet.

Total stopping distance - The total minimum distance your vehicle has traveled, in ideal conditions; with everything considered, including perception distance, reaction distance and braking distance, until you can bring your vehicle to a complete stop. At 55 mph, your vehicle will travel a minimum of 419 feet. (See Figure 2.11.)

The Effect Of Speed And Weight On Stopping Distance

The Effect of Speed on Stopping Distance - The faster you drive, the greater the impact or striking power of your vehicle. When you double your speed from 20 to 40 mph the impact is four times greater. The braking distance is also four times longer. Triple the speed from 20 to 60 mph and the impact and braking distance is nine times greater. At 60 mph, your stopping distance is greater than the length of a football field. Increase the speed to 80 mph, and the impact and braking distance are 16 times greater than at 20 mph. High speeds greatly increase the severity of crashes and stopping distances. By slowing down, you can reduce braking distance.

The Effect of Vehicle Weight on Stopping Distance - The heavier the vehicle, the more work the brakes must do to stop it and the more heat they absorb. The brakes, tires, springs and shock absorbers on heavy vehicles are designed to work best when the vehicle is fully loaded. Empty trucks require greater stopping distances because an empty vehicle has less traction.

Identifying Slippery Surfaces

Sometimes it is hard to know if the road is slippery. Following are signs of slippery roads:

  • Shaded Areas - Shady parts of the road will remain icy and slippery long after open areas have melted.
  • Bridges - When the temperature drops, bridges will freeze before the road will. Be especially careful when the temperature is close to 32F.
  • Melting Ice - Slight melting will make ice wet. Wet ice is much more slippery than ice that is not wet.
  • Black Ice - Black ice is a thin layer that is clear enough that you can see the road underneath it. It makes the road look wet. Any time the temperature is below freezing and the road looks wet, watch out for black ice.
  • Vehicle Icing - An easy way to check for ice is to open the window and feel the front of the mirror, mirror support or antenna. If there's ice on these, the road surface is probably starting to ice up.
  • Just After Rain Begins - Right after it starts to rain, the water mixes with oil left on the road by vehicles. This makes the road very slippery. If the rain continues, it will wash the oil away.
  • Hydroplaning - In some weather, water or slush collects on the road. When this happens, your vehicle can hydroplane. It is like water skiing - the tires lose contact with the road and have little or no traction. You may not be able to steer or brake. You can regain control by releasing the accelerator and pushing in the clutch. This will slow your vehicle and let the wheels turn freely. If the vehicle is hydroplaning, do not use the brakes to slow down. If the drive wheels start to skid, push in the clutch to let them turn freely

More Questions You Should Know Before Taking The CDL Exam

  • 1. How far ahead does the manual say you should look?
  • 2. What are two main things to look for ahead?
  • 3. What's your most important way to see the sides and rear of your vehicle?
  • 4. What does "communicating" mean in safe driving?
  • 5. Where should your reflectors be placed when stopped on a divided highway?
  • 6. What three things add up to total stopping distance?
  • 7. If you go twice as fast, will your stopping distance increase by two or four times?
  • 8. Empty trucks have the best braking. True or False?
  • 9. What is hydroplaning?
  • 10. What is "black ice?”

Making Turns Safely

Right Turns:

Following are some rules to help prevent right-turn crashes:

  • Turn slowly to give yourself and others more time to avoid problems.
  • If you are driving a truck or bus that cannot make the right turn without swinging into another lane, turn wide as you complete the turn. Keep the rear of your vehicle close to the curb. This will stop other drivers from passing you on the right.
  • Do not turn wide to the left as you start the turn. A following driver may think you are turning left and try to pass you on the right. You may crash into the other vehicle as you complete your turn.
  • If you must cross into the oncoming lane to make a turn, watch out for vehicles coming toward you. Give them room to go by or to stop. However, do not back up for them, because you might hit someone behind you.

Left Turns:

  • On a left turn, make sure you have reached the center of the intersection before you start the left turn. If you turn too soon, the left side of your vehicle may hit another vehicle because of off tracking.
  • If there are two turning lanes, always take the right turn lane. Do not start in the inside lane because you may have to swing right to make the turn. Drivers on your left can be more readily seen.

More Questions You Should Be Able To Answer

  • 1. How do you find out how many seconds of following distance space you have?
  • 2. If you are driving a 30-foot vehicle at 55 mph, how many seconds of following distance should you allow?
  • 3. You should decrease your following distance if somebody is following you too closely. True or False?
  • 4. If you swing wide to the left before turning right, another driver may try to pass you on the right. True or False?
  • 5. What is a hazard?
  • 6. Why make emergency plans when you see a hazard?

Distracted Driving

Whenever you are driving a vehicle and your attention is not on the road, you are putting yourself, your passengers, other vehicles and pedestrians in danger. Distracted driving can result when performing any activity that may shift your full attention from the driving task. Taking your eyes off the road or hands off the steering wheel presents obvious driving risks. Mental activities that take your mind away from driving are just as dangerous. Your eyes can gaze at objects in the driving scene but fail to see them because your attention is distracted elsewhere.

Activities that can distract your attention include: talking to passengers; adjusting the radio, CD player or climate controls; eating, drinking or smoking; reading maps or other literature; picking up something that fell; reading billboards and other road advertisements; watching other people and vehicles including aggressive drivers; talking on a cellphone or CB radio; using telematic devices (such as navigation systems, pagers, etc.); daydreaming or being occupied with other mental distractions.

Railroad Crossings

Railroad crossings with steep approaches can cause your unit to hang up on the tracks. Never permit traffic conditions to trap you in a position where you have to stop on the tracks. Be sure you can get all the way across the tracks before you start across. It takes a typical tractor-trailer unit at least 14 seconds to clear a single track and more than 15 seconds to clear a double track.

Do not shift gears while crossing railroad tracks.

Mountain Driving

Select the Right Gear Before Starting Down the Grade.

You must use the braking effect of the engine as the principal way of controlling your speed. The braking effect of the engine is greatest when it is near the governed rpms and the transmission is in the lower gears. Save your brakes so you will be able to slow or stop as required by road and traffic conditions.

Shift the transmission to a low gear before starting down the grade. Do not try to downshift after your speed has already built up. You will not be able to shift into a lower gear. You may not even be able to get back into any gear and all engine braking effect will be lost. Forcing an automatic transmission into a lower gear at high speed could damage the transmission and also lead to loss of all engine braking effect.

With older trucks, a rule for choosing gears is to use the same gear going down a hill that you would need to climb the hill. However, new trucks have low friction parts and streamlined shapes for fuel economy. They may also have more powerful engines. This means they can go up hills in higher gears and have less friction and air drag to hold them back going down hills. For that reason, drivers of modern trucks may have to use lower gears going down a hill than would be required to go up the hill. You should know what is right for your vehicle.

Proper Mountain Braking Techniques

Remember — The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine. Once the vehicle is in the proper low gear, the following are the proper braking techniques:

  • 1.Apply the brakes just hard enough to feel a definite slowdown.
  • 2. When your speed has been reduced to approximately 5 mph below your "safe" speed, release the brakes.
  • 3. When your speed has increased to your "safe" speed, repeat Steps 1 and 2.

For example, if your "safe" speed is 40 mph, you would not apply the brakes until your speed reaches 40 mph. You now apply the brakes hard enough to gradually reduce your speed to 35 mph and then release the brakes. Repeat this as often as necessary until you have reached the end of the downgrade.

More Questions You Should Know

  • 1. What factors determine your selection of a "safe" speed when going down a long, steep downgrade?
  • 2. Why should you be in the proper gear before starting down a hill?
  • 3. Describe the proper braking technique when going down a long, steep downgrade.
  • 4. What type of vehicles can get stuck on a railroad-highway crossing?
  • 5. How long does it take for a typical tractor-trailer unit to clear a double track?

Stopping Quickly

If somebody suddenly pulls out in front of you, your natural response is to hit the brakes. This is a good response if there is enough distance to stop and you use the brakes correctly. You should brake in a way that will keep your vehicle in a straight line and allow you to turn if it becomes necessary. You can use the "controlled braking" method or the "stab braking" method.

Controlled braking: With this method, you apply the brakes as hard as you can without locking the wheels. Keep steering wheel movements very small while doing this. If you need to make a larger steering adjustment or if the wheels lock, release the brakes. Re-apply the brakes as soon as you can.

Stab braking:

  • Apply your brakes all the way.
  • Release brakes when wheels lock up.
  • As soon as the wheels start rolling, apply the brakes fully again. (It can take up to one second for the wheels to start rolling after you release the brakes. If you re-apply the brakes before the wheels start rolling, the vehicle won't straighten out.)

Do not jam on the brakes: Emergency braking does not mean pushing down on the brake pedal as hard as you can. That will only keep the wheels locked up and cause a skid. If the wheels are skidding, you cannot control the vehicle.

Becoming Sleepy Behind The Wheel

When you are sleepy, trying to "push on" is far more dangerous than most drivers think. It is a major cause of fatal accidents. Here are some important rules to follow:

  • Stop to Sleep: When your body needs sleep, sleep is the only thing that will work. If you have to make a stop anyway, make it whenever you feel the first signs of sleepiness, even if it is earlier than you planned. By getting up a little earlier the next day, you can keep on schedule without the danger of driving while you are not alert.
  • Take a Nap: If you cannot stop for the night, at least pull off at a safe place, such as a rest area or truck stop, and take a nap. A nap as short as a half-hour will do more to overcome fatigue than a half-hour coffee stop.
  • Avoid Drugs: There are no drugs that can overcome being tired. While they may keep you awake for a while, they won't make you alert. And eventually, you will be even more tired than if you had not taken them at all. Sleep is the only thing that can overcome fatigue.

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