Simulado CDL Combination Vehicles

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Todas as 15 questões de uma vez

Prefere ler antes de jogar? Todas as questões da amostra estão listadas abaixo. As respostas e as explicações ficam fechadas até você abrir.

1. 1. Which pair of habits does the most to keep a loaded combination vehicle from rolling over?

   • A. Load the heaviest cargo on top and brake hard just before each curve
   • B. Push the load toward one side wall so it cannot shift, and keep your speed up through ramps
   • C. Keep the cargo as close to the ground as possible, and drive slowly around turns
   • D. Run the trailer a little overloaded so it settles lower on its springs
   Mostrar resposta e explicação

   Resposta: C. Keep the cargo as close to the ground as possible, and drive slowly around turns

   Stacking cargo high raises the center of gravity, and a higher center of gravity tips more easily, which is why a fully loaded rig is far more likely to roll in a crash than an empty one. Keeping the load low and slowing down for corners, ramps and off ramps are the two things a driver controls directly. Centering the load matters too, because a load pushed to one side makes the trailer lean and starts the roll for you.

2. 2. You are making a tight right turn and cannot finish it without using part of the next lane. What does off-tracking tell you to do?

   • A. Swing wide to the left before you start the turn, so the trailer has room
   • B. Start the turn close to the curb and swing wide as you complete it, keeping the rear near the curb
   • C. Turn from the left lane every time, because the trailer wheels track outside the tractor wheels
   • D. Nothing, since off-tracking only affects backing
   Mostrar resposta e explicação

   Resposta: B. Start the turn close to the curb and swing wide as you complete it, keeping the rear near the curb

   Going around a corner, the rear wheels follow a tighter path than the front wheels, and the rear wheels of the trailer cut in the most. So you have to steer the front end wide enough that the rear does not climb the curb. Swinging left first invites a following driver to think you are turning left and slip up your right side, which is where your trailer is about to be. Turning wide at the end instead, with the rear kept close to the curb, blocks that gap.

3. 3. Rearward amplification, the crack the whip effect, is greatest in which of these?

   • A. A bobtail tractor with no trailer
   • B. A three axle tractor pulling one short semitrailer
   • C. A five axle tractor semitrailer with a 45 foot trailer
   • D. The last trailer of a set of triples
   Mostrar resposta e explicação

   Resposta: D. The last trailer of a set of triples

   In a quick lane change, each trailer swings harder than the unit ahead of it, so the more trailers you add, the more the back one whips. The CDL manual charts this: a five axle tractor semitrailer sits near the bottom of the scale and triples sit at the top, roughly three and a half times as easy to roll at the last trailer. That is why you steer gently and smoothly, look far enough ahead to avoid sudden lane changes, and slow down before a turn rather than during it.

4. 4. You brake hard on a wet ramp and see in your mirror that the trailer is starting to swing out. What is the first thing you do?

   • A. Release the brakes so the trailer wheels can roll and get traction back
   • B. Press the brake pedal harder to pull the trailer back in line
   • C. Apply the trailer hand valve to straighten the rig out
   • D. Set the parking brake and steer toward the shoulder
   Mostrar resposta e explicação

   Resposta: A. Release the brakes so the trailer wheels can roll and get traction back

   A trailer jackknife starts when the trailer wheels lock up and slide, which happens most easily when the trailer is empty or lightly loaded. Locked wheels cannot steer or track, so the fix is to stop braking and let them roll again. Once they grip, the trailer follows the tractor and straightens itself out. Checking your mirrors every time you brake hard is what buys you the time to catch it, because once the trailer leaves your lane it is very hard to save.

5. 5. What is the trailer hand valve, also called the trolley valve or Johnson bar, actually for?

   • A. Holding the rig on a grade instead of using the parking brakes
   • B. Straightening the rig out when the trailer begins to swing
   • C. Testing the trailer brakes, and nothing else
   • D. Releasing the trailer spring brakes before you pull away
   Mostrar resposta e explicação

   Resposta: C. Testing the trailer brakes, and nothing else

   The hand valve applies the trailer brakes only, which is exactly the condition that starts a trailer skid, so it has no place in normal driving. The foot brake sends air to every brake on the rig, tractor and trailer together, and is far less likely to jackknife you. It is also wrong for parking, because on a trailer without spring brakes the air can leak away overnight and release the brakes, so use the parking brakes and chock the wheels.

6. 6. You crawl under with a flashlight after coupling and see a gap between the upper and lower fifth wheel. What does that mean?

   • A. The coupling is wrong, and the kingpin may be sitting on top of the closed jaws
   • B. It is normal, because the plate needs clearance for grease
   • C. The trailer is loaded too heavy and is lifting the plate slightly
   • D. Nothing, as long as the tug test already passed
   Mostrar resposta e explicação

   Resposta: A. The coupling is wrong, and the kingpin may be sitting on top of the closed jaws

   There should be no visible space at all between the upper and lower fifth wheel. A gap usually means the jaws closed before the kingpin dropped in, so the pin is resting on top of them instead of being captured, and the trailer can come loose very easily. This is one of the reasons you shut the engine off, take the key with you and look with a light rather than trusting the tug test alone. If the coupling is not right, do not drive it, get it fixed.

7. 7. When you look into the back of the fifth wheel, the locking jaws should be closed around which part of the kingpin?

   • A. The head
   • B. The shank
   • C. The base plate
   • D. The trailer apron
   Mostrar resposta e explicação

   Resposta: B. The shank

   The kingpin has a base, a narrower shank and a wider head at the bottom. The jaws are meant to wrap the shank, so the head sits below them and cannot pull up through. Jaws closed around the head look locked from a distance but hold almost nothing. While you are under there, also confirm the locking lever is in the lock position and the safety latch is seated over it, since on some fifth wheels that catch has to be placed by hand.

8. 8. You couple to a modern trailer with spring brakes and accidentally cross the air lines. What happens?

   • A. The trailer brakes drag but the rig still rolls normally
   • B. Nothing changes, because both lines carry the same air
   • C. The marker lights fail while the brakes keep working
   • D. Supply air goes to the service line, the trailer tanks never charge, and the spring brakes will not release
   Mostrar resposta e explicação

   Resposta: D. Supply air goes to the service line, the trailer tanks never charge, and the spring brakes will not release

   Air meant to fill the trailer tanks gets sent down the service line instead, so there is never enough pressure to push the spring brakes off. If you push the trailer air supply control and the spring brakes stay set, check your glad hand connections first. The dangerous version is an older trailer with no spring brakes and a drained tank: crossed lines there let you drive away with no trailer brakes at all, which is why you shut the engine off and listen for the trailer brakes applying and releasing before you move.

9. 9. A trailer breaks away and tears the emergency line apart. What happens next?

   • A. The tractor loses its air too, and the driver is left with no brakes
   • B. The tractor protection valve closes to keep air in the tractor, and the trailer emergency brakes come on
   • C. Only the trailer lights go out, because the emergency line is electrical
   • D. The service line keeps the trailer brakes released until the trailer tank drains
   Mostrar resposta e explicação

   Resposta: B. The tractor protection valve closes to keep air in the tractor, and the trailer emergency brakes come on

   The emergency line does two jobs: it charges the trailer air tanks and it holds the trailer emergency brakes off. Lose pressure in it and those brakes apply on their own. At the tractor end, the tractor protection valve shuts so the tractor keeps the air it needs for its own brakes, and the red eight sided trailer air supply knob pops out. That valve closes by itself once pressure falls into the range the manufacturer specifies, usually somewhere between 20 and 45 psi.

10. 10. Before you back the tractor under the trailer, which of these must already be done?

    Marque todas as opções corretas.

    • A. The trailer wheels are chocked, or the trailer spring brakes are set
    • B. The tractor is lined up directly in front of the trailer, not at an angle
    • C. The trailer is set low enough that the tractor lifts it slightly as it backs under
    • D. The landing gear is fully raised and the crank handle is secured
    • E. The electrical cord is plugged into the trailer and the safety catch is fastened
    Mostrar resposta e explicação

    Resposta: A. The trailer wheels are chocked, or the trailer spring brakes are set, B. The tractor is lined up directly in front of the trailer, not at an angle, C. The trailer is set low enough that the tractor lifts it slightly as it backs under

    Chocking or setting the trailer brakes keeps the trailer from walking away as the tractor pushes into it. Backing under at an angle can shove the trailer sideways and snap the landing gear, so line up straight and check both sides in your mirrors. Trailer height matters in both directions: too low and you hit the trailer nose, too high and the pin will not seat. The electrical cord goes on after you have crawled under and inspected the coupling, and the landing gear comes up last of all.

11. 11. Which walkaround checks are added because the vehicle is a combination, and are not part of a straight truck inspection?

    Marque todas as opções corretas.

    • A. The lower fifth wheel is mounted securely, greased, with no visible space against the upper plate
    • B. The air and electrical lines are connected, undamaged, and secured with enough slack for turns
    • C. The landing gear is fully raised and undamaged, with the crank handle in place and secured
    • D. The windshield wipers are secure and the blades are not torn
    • E. The steering wheel has no more than the allowed amount of free play
    Mostrar resposta e explicação

    Resposta: A. The lower fifth wheel is mounted securely, greased, with no visible space against the upper plate, B. The air and electrical lines are connected, undamaged, and secured with enough slack for turns, C. The landing gear is fully raised and undamaged, with the crank handle in place and secured

    You still run the same seven step inspection, plus a set of items that only exist once there is a trailer behind you: the coupling system, the lines that cross to the trailer, and the landing gear. On a sliding fifth wheel you also confirm every locking pin is present and locked, and that the fifth wheel is not so far forward that the tractor frame will strike the landing gear in a sharp turn. Wipers and steering play belong to the ordinary inspection you already do on any vehicle.

12. 12. You are dropping a loaded trailer. Which of these are the correct actions?

    Marque todas as opções corretas.

    • A. Shut off the trailer air supply to lock the trailer brakes, back up gently against the kingpin, then set the parking brake while the tractor is still pushing
    • B. After the landing gear makes firm contact with the ground, crank a few extra turns in low gear to take some weight off the fifth wheel
    • C. Pull forward only until the fifth wheel clears, leaving the tractor frame under the trailer, then get out and check the supports
    • D. Pull the release handle and drive straight out in one move, since the landing gear will catch the trailer
    • E. Leave the air lines connected so the trailer keeps its brakes applied after you drive away
    Mostrar resposta e explicação

    Resposta: A. Shut off the trailer air supply to lock the trailer brakes, back up gently against the kingpin, then set the parking brake while the tractor is still pushing, B. After the landing gear makes firm contact with the ground, crank a few extra turns in low gear to take some weight off the fifth wheel, C. Pull forward only until the fifth wheel clears, leaving the tractor frame under the trailer, then get out and check the supports

    Backing gently against the kingpin takes the load off the locking jaws so the release handle will move, and setting the parking brake holds it there. On a loaded trailer, a few extra cranks lift a little weight off the fifth wheel, which makes the jaws easier to open now and easier to couple next time, though you never lift the trailer off the plate. Stopping with the tractor frame still under the trailer means that if the landing gear sinks or collapses, the trailer lands on your frame instead of the ground.

13. 13. Complete the sentence.

    On a rig pulling more than one trailer, the shut-off valves in the service and supply lines must be _____ at the rear of the last trailer and _____ on all the others.

    Opções para a lacuna 1: open, closed, removed

    Opções para a lacuna 2: open, closed, capped

    Mostrar resposta e explicação

    Resposta: closed, open

    Those valves exist so the lines can be sealed off when nothing is being towed behind that trailer. Leave the last one open and air escapes out the back, so nothing downstream of the leak builds pressure. Leave a middle one closed and the trailers behind it never get air at all. You check this by opening the valve at the rear of the last trailer and listening for air, which proves the whole system is charged all the way back.

14. 14. Complete the sentence.

    To check that the coupling caught, raise the landing gear slightly off the ground, keep the trailer brakes locked, and _____.

    Opções para a lacuna 1: pull the tractor gently forward, rock the tractor back and forth in reverse, release the parking brake and let the rig roll backward, apply full throttle against the trailer

    Mostrar resposta e explicação

    Resposta: pull the tractor gently forward

    A gentle tug against locked trailer brakes is the quickest proof that the jaws actually captured the kingpin rather than sliding past it. Keep it gentle, because a hard pull against a bad coupling is how a trailer ends up on the ground. Passing the tug is not the end of it either. You still put the transmission in neutral, set the parking brakes, shut the engine off, take the key with you and inspect the coupling by eye before anything else.

15. 15. Complete the sentence.

    The service line, which carries the air your foot brake meters out to the trailer, is usually color coded _____, while the emergency line, which fills the trailer air tanks and holds the emergency brakes off, is usually color coded _____.

    Opções para a lacuna 1: blue, red, green, yellow

    Opções para a lacuna 2: blue, red, black

    Mostrar resposta e explicação

    Resposta: blue, red

    The service line is also called the control line or signal line, and the pressure in it rises and falls with how hard you press the pedal, which is what tells the relay valves how much brake to apply. The emergency line is also called the supply line, and it does the two jobs above at once. Colors are a helpful habit and not a guarantee, so read the metal tags stamped service and emergency when they are fitted, and clean the rubber seals before you couple the glad hands.

O que a prova de combination vehicles cobra de verdade

A prova de combination vehicles é uma das provas teóricas que você faz no órgão de habilitação do seu estado, nos Estados Unidos, e todo candidato à Class A a encara. Ela é separada da prova de general knowledge, separada da prova de air brakes e separada do endorsement de doubles and triples, então a maioria dos candidatos à Class A acaba fazendo pelo menos três provas escritas antes de encostar em um caminhão. Os estados escrevem os próprios conjuntos de questões a partir do mesmo manual modelo de CDL, então o número de questões, o tempo limite, a taxa e em quanto tempo você pode refazer depois de reprovar variam de estado para estado. A nota de corte não varia do mesmo jeito. As regras federais exigem que você acerte pelo menos 80 por cento das questões em cada prova teórica, então um estado que te dá 20 questões está deixando você errar quatro, e um estado que te dá 50 está deixando você errar dez.

O conteúdo vem da Seção 6 do manual de CDL do seu estado e se divide em cinco partes. Dirigir combination vehicles com segurança cobre risco de capotamento e centro de gravidade, esterçar com suavidade e o efeito chicote, frear cedo, reboques de baixa altura livre encalhando em passagens de nível elevadas, derrapagem do reboque, fazer curvas abertas por causa do off-tracking, e dar ré com um reboque. Freios a ar de combination vehicles cobre a válvula manual do reboque, a tractor protection valve, o controle de fornecimento de ar do reboque, as linhas de serviço e de emergência, os glad hands, os reservatórios de ar do reboque e as válvulas de bloqueio. Os freios ABS ganham uma parte curta só deles, quase toda sobre o que o ABS não faz por você. Depois vêm os passos numerados de engate e desengate, e os itens extras que entram na volta de inspeção quando há um reboque atrás de você.

Os passos de engate e desengate merecem a maior fatia do seu tempo de estudo, porque eles aparecem duas vezes. São cobrados nesta prova escrita, e depois você tem que achar, tocar e nomear as peças do engate em voz alta durante a parte de inspeção pré-viagem do skills test. Outras duas coisas vale resolver cedo. Baixe o manual do seu próprio estado em vez de um PDF genérico, porque o seu estado escreve as questões a partir da versão que ele publica e a redação vai bater. E veja como você está em relação ao entry level driver training. Desde fevereiro de 2022, as regras federais exigem treinamento com um provedor do registro federal antes de você poder fazer o skills test para uma primeira habilitação Class A, e isso é um passo separado de qualquer uma das provas teóricas.

Como usar esta amostra e como estudar a Seção 6

Estas 15 questões se apoiam no raciocínio por trás das regras, não no vocabulário. Elas perguntam por que um reboque tomba antes do cavalo mecânico, por que você solta o freio em uma derrapagem do reboque em vez de frear mais, o que acontece de fato quando os glad hands são cruzados, e em que ordem vão os passos do engate. É essa a parte que a prova escrita premia, e é também a parte que te mantém em pé em uma alça molhada de noite. As questões misturam os formatos que uma prova teórica usa, incluindo marcar todas as corretas e completar a lacuna, porque escolher três respostas certas entre cinco é uma checagem mais dura e mais honesta do que você sabe do que escolher uma entre quatro.

Faça tudo de uma vez, sem consultar anotações, e depois leia a explicação de cada questão, inclusive das que você acertou. Trate uma resposta errada como um tema, não como um fato solto. Se você errou a questão das linhas de ar cruzadas e a da tractor protection valve, volte e revise a subseção inteira de linhas de ar de uma vez, porque a linha de serviço e a de emergência só fazem sentido em par. O mesmo vale para capotamento e amplificação para trás, que são duas visões de um mesmo problema, já que uma carga alta e um reboque chicoteando terminam ambos com o baú deitado. Nada aqui é pontuado nem guardado em lugar nenhum, então não custa nada fazer sem preparo e descobrir o que você ainda não sabe.

Para os passos do engate, ler não basta. Escreva os dezesseis passos de engate e os dez passos de desengate de memória, na ordem, até conseguir fazer isso sem olhar, e depois diga em voz alta enquanto anda em volta de uma carreta de verdade, se você tiver acesso a uma. A ordem carrega a lógica de segurança, e é a lógica que faz a ordem grudar. Você calça as rodas antes de posicionar o cavalo mecânico, trava os freios do reboque antes de dar ré por baixo dele, entra embaixo com uma lanterna e confere as garras do fifth wheel, o prato de engate, antes de plugar o cabo elétrico, e levanta o landing gear, o pé de apoio, por último. Acerte a ordem e boa parte das questões individuais se responde sozinha.

Como a StudyPDF cria simulados completos do seu próprio material de CDL

Quinze questões mostram onde você está inseguro. Elas não deixam você pronto sozinhas, e um banco de questões genérico se afasta da redação que o manual do seu estado usa, que é a redação de onde a sua prova sai. Depois de saber onde estão suas áreas fracas, o que você precisa é de volume nessas áreas específicas, tirado das páginas que te entregaram de verdade.

A StudyPDF segue outro caminho. Você envia o manual de CDL do seu estado, a apostila da Seção 6 da sua escola, ou as anotações que o instrutor te deu, e o Bo, o agente de estudo, cria simulados completos a partir exatamente dessas páginas. Cada questão é baseada no seu material, e cada explicação cita de onde vem a resposta, então dá para ir direto à fonte quando algo parecer estranho. Você pode gerar simulados novos quantas vezes quiser, restringir a uma área só, como engate e desengate ou as linhas de ar, e acompanhar quais temas você continua errando.

Você não precisa enviar nada para começar. Se não tem nenhum arquivo à mão, diga um tema, por exemplo engatar um cavalo mecânico a um semirreboque, a tractor protection valve ou como evitar a derrapagem do reboque, e o Bo escreve um simulado a partir disso. Isso ajuda quando você está esperando a apostila da escola, ou estudando por um manual que só tem em papel. Comece grátis.