Test de práctica CDL General Knowledge

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Las 15 preguntas de un vistazo

¿Prefieres leer antes de jugar? Abajo están todas las preguntas de la muestra. Las respuestas y explicaciones quedan plegadas hasta que las abras.

1. 1. Federal rules require a commercial vehicle to carry a set of emergency equipment. Which set is correct?

   • A. A first aid kit, a tire pressure gauge and a flashlight
   • B. Two red flags, jumper cables and a spare fuel filter
   • C. Three red reflective warning triangles, at least one charged and rated fire extinguisher, and spare electrical fuses if the vehicle uses them
   • D. A wheel chock, a reflective vest and a spare drive belt
   Ver respuesta y explicación

   Respuesta: C. Three red reflective warning triangles, at least one charged and rated fire extinguisher, and spare electrical fuses if the vehicle uses them

   You check this equipment during the in-cab step of the seven step inspection, before you check the lights and start the walkaround. Warning devices mark your vehicle for other drivers when you have to stop on the shoulder, the extinguisher has to be charged and rated for what you haul, and fuses only apply if the vehicle uses them, since many use circuit breakers instead. A first aid kit and a flashlight are smart to carry, but they are not what the rule asks for.

2. 2. You are on the walkaround part of your pre-trip inspection. Which findings mean the vehicle should not go out until it is repaired?

   Marca todas las que correspondan.

   • A. A steering axle tire measuring 3/32 inch of tread
   • B. A recapped tire on a drive axle
   • C. A cut in a tire deep enough to show the body ply underneath
   • D. A rear tire measuring 5/32 inch of tread
   • E. A crack running across the rim of a wheel
   Ver respuesta y explicación

   Respuesta: A. A steering axle tire measuring 3/32 inch of tread, C. A cut in a tire deep enough to show the body ply underneath, E. A crack running across the rim of a wheel

   Front tires carry the steering and the most load per tire, so they need more tread than the rest, and 3/32 inch is under the minimum. Any tire with fabric, body ply or belt material showing is unsafe no matter how much tread is left, and a cracked or bent rim can let a tire come off the wheel. A recapped tire is legal on a drive axle, and 5/32 inch on a rear tire is above the minimum, so neither of those grounds the vehicle.

3. 3. Complete the sentence.

   Federal rules set a minimum tread depth of _____ inch on the tires of the steering axle and _____ inch on every other tire.

   Opciones para el hueco 1: 2/32, 4/32, 6/32, 8/32

   Opciones para el hueco 2: 1/32, 2/32, 4/32

   Ver respuesta y explicación

   Respuesta: 4/32, 2/32

   Measure in a major groove, not on a rib or a wear bar, and check more than one spot, since uneven wear can leave one shoulder legal and the other bald. Tread depth is one of the few numbers the general knowledge test asks you for directly. Uneven wear is also a clue to something else, so a front tire wearing on one edge usually means an alignment or inflation problem rather than a tire problem.

4. 4. You have to back into a space and you can choose which side to back toward. What is the safer choice and why?

   • A. Back toward the driver side, because you can see that side of the vehicle directly as well as in the mirror
   • B. Back toward the passenger side, because that mirror is convex and shows a wider view
   • C. Either side is equally safe as long as you use both mirrors
   • D. Back toward the passenger side, because oncoming traffic sees you sooner
   Ver respuesta y explicación

   Respuesta: A. Back toward the driver side, because you can see that side of the vehicle directly as well as in the mirror

   Backing toward the passenger side is blind side backing, and it forces you to trust one mirror for a whole quarter of the vehicle. A wider mirror view does not make up for losing the direct look. Whichever side you use, get out and walk the area first, back slowly, and if you have a helper, agree on hand signals in advance and keep the helper somewhere you can see in the mirror, with a clear signal that means stop.

5. 5. You are making a tight right turn at an intersection in a long vehicle. What is the correct technique?

   • A. Swing wide to the left first so the rear has room, then complete the turn
   • B. Move to the center of the road before the turn so nobody can come up on your right
   • C. Turn from the left lane whenever the corner looks tight
   • D. Keep the rear of the vehicle close to the curb and swing wide only as you complete the turn
   Ver respuesta y explicación

   Respuesta: D. Keep the rear of the vehicle close to the curb and swing wide only as you complete the turn

   The rear wheels follow a tighter path than the front wheels, which is called off tracking, so a long vehicle has to turn wide somewhere. Doing it at the end keeps the gap on your right closed. If you swing left first, a driver behind you may read it as a left turn or slip into the space on your right and get squeezed against the curb. If you cannot make the turn without crossing into the oncoming lane, wait until that lane is clear rather than starting the turn and hoping.

6. 6. Complete the sentence.

   Below 40 mph, allow one second of following distance for every _____ feet of vehicle length. At 55 mph, a 60 foot combination should therefore keep at least _____ seconds of space ahead.

   Opciones para el hueco 1: 5, 10, 15, 20

   Opciones para el hueco 2: 4, 5, 6, 7

   Ver respuesta y explicación

   Respuesta: 10, 7

   Sixty feet divided by ten gives six seconds, and above 40 mph you add one more second, which makes seven. To count it, watch the vehicle ahead pass a fixed object such as a sign or an overpass shadow, then count the seconds until the front of your vehicle reaches the same point. Add more space on wet or icy roads, at night, and any time you are following something you cannot see past.

7. 7. Total stopping distance is the sum of which three distances?

   • A. Perception distance, braking distance and skid distance
   • B. Perception distance, reaction distance and braking distance
   • C. Reaction distance, braking distance and following distance
   • D. Sight distance, reaction distance and braking distance
   Ver respuesta y explicación

   Respuesta: B. Perception distance, reaction distance and braking distance

   Perception distance is how far you travel from the moment your eyes see a hazard until your brain recognizes it. Reaction distance is how far you travel from that recognition until your foot reaches the brake. Braking distance is how far the vehicle travels once the brakes are actually working. The model manual puts all three together at 55 mph on dry pavement with good brakes at roughly 335 feet, which is longer than a football field, and that is why looking far ahead buys you more than any braking technique.

8. 8. Which statements about speed and stopping are true?

   Marca todas las que correspondan.

   • A. Braking distance grows in step with speed, so twice the speed means twice the distance
   • B. Doubling your speed roughly quadruples the braking distance
   • C. An empty truck can need a longer stopping distance than a loaded one
   • D. Wet pavement makes no difference as long as the tires have legal tread
   • E. Posted curve speeds are set with cars in mind, so a heavy vehicle often has to go slower than the sign
   Ver respuesta y explicación

   Respuesta: B. Doubling your speed roughly quadruples the braking distance, C. An empty truck can need a longer stopping distance than a loaded one, E. Posted curve speeds are set with cars in mind, so a heavy vehicle often has to go slower than the sign

   Braking distance grows with the square of speed, so the jump from 20 to 40 mph costs you about four times the distance, not two. An empty truck feels nimble but has less weight pressing its tires down, and its brakes and suspension are built for a load, so it can skid and stop poorly. On wet roads the usual guidance is to cut your speed by about a third, on packed snow by about half, and on ice to slow to a crawl and get off the road as soon as you safely can.

9. 9. How far ahead should you be looking while you drive?

   • A. About 2 to 4 seconds ahead, since that is where a hazard would actually reach you
   • B. Only as far as your headlights reach, so you do not miss what is close
   • C. About 12 to 15 seconds ahead, which is roughly a quarter mile at highway speed
   • D. About 30 seconds ahead, which is roughly a mile at highway speed
   Ver respuesta y explicación

   Respuesta: C. About 12 to 15 seconds ahead, which is roughly a quarter mile at highway speed

   Twelve to fifteen seconds is about one city block in town and about a quarter mile on the highway. At that range you still have time to slow smoothly or change lanes instead of braking hard. Looking far ahead does not mean staring at one point, so keep scanning near and far and check your mirrors every five to eight seconds, more often when traffic is heavy or you are near other vehicles.

10. 10. Why should you shift into a low gear before you start down a long, steep grade?

    • A. Because engine braking then helps hold your speed, and the transmission may not let you get into a low gear once you are already rolling fast
    • B. Because a low gear increases air flow through the radiator and stops the engine overheating
    • C. Because the higher the gear, the harder the service brakes hold
    • D. Because a low gear locks the drive axles together and gives you extra traction
    Ver respuesta y explicación

    Respuesta: A. Because engine braking then helps hold your speed, and the transmission may not let you get into a low gear once you are already rolling fast

    Gravity keeps adding speed the whole way down, so the gear does the steady work and the brakes are there to supplement it, not to carry the descent alone. Brakes that are held on continuously heat up and fade, and by the time you notice that they are fading you have very little left. Your safe speed depends on the weight, the length and steepness of the grade, the road surface and the weather, so read the signs at the top and know where the escape ramps are before you need one.

11. 11. Complete the sentence.

    Cargo held down with tiedowns needs at least one tiedown for every _____ feet of cargo, and no load, however short, may have fewer than _____ tiedowns.

    Opciones para el hueco 1: 5, 8, 10, 12

    Opciones para el hueco 2: one, two, three

    Ver respuesta y explicación

    Respuesta: 10, two

    The count is only half of it, since the combined working load limit of the tiedowns has to be at least half the weight of the cargo they hold. Securement is also the driver's job even when someone else loaded the trailer, so inspect the load before you leave, again within the first 50 miles, and then every 150 miles or every 3 hours, whichever comes first. Weight that sits too high raises the center of gravity and makes a rollover in a curve or an exit ramp much easier.

12. 12. A fire starts in the wiring behind your dashboard. Which extinguisher is right, and what must you not do?

    • A. A class A extinguisher, and do not aim at the base of the flames
    • B. Water, and do not open the hood
    • C. A class D extinguisher, and do not shut the engine off
    • D. A B:C or A:B:C extinguisher, and do not put water on an electrical fire
    Ver respuesta y explicación

    Respuesta: D. A B:C or A:B:C extinguisher, and do not put water on an electrical fire

    Class A covers ordinary combustibles like wood, paper and cloth, class B covers burning liquids such as fuel and grease, class C covers electrical fires and class D covers burning metals. Water conducts electricity and it spreads a liquid fire instead of putting it out, so the B:C rating is what matters here. Before you use it, pull well off the road away from buildings and other vehicles, shut the engine off, call for help, then stay upwind, aim at the base of the flames and use short bursts. Only fight a fire that is small enough for you to handle.

13. 13. You are approaching a railroad crossing with no gate and a clear view of the track. What should you do?

    • A. Shift down as you reach the rails so you can accelerate away quickly
    • B. Stay in one gear the whole way across, and do not start across unless you can clear the far side without stopping
    • C. Stop on the near rail, look both ways, then move on
    • D. Speed up so you spend less time on the tracks
    Ver respuesta y explicación

    Respuesta: B. Stay in one gear the whole way across, and do not start across unless you can clear the far side without stopping

    Changing gears on the crossing is how drivers end up stalled on the rails, so pick your gear before the tracks and hold it. A tractor and trailer needs roughly 14 to 15 seconds to clear a single track, longer for a double track, so you have to see room for the whole vehicle on the far side before you start. Watch for raised or humped crossings if you drive anything low slung, and remember that buses and some placarded loads have to stop at every crossing whether or not a train is coming.

14. 14. Which statements about skids are true?

    Marca todas las que correspondan.

    • A. Most skids happen because the vehicle was going too fast for the conditions
    • B. Black ice is easy to spot because it turns the pavement white
    • C. Pressing harder on the accelerator is the quickest way to straighten out a skid
    • D. In a drive wheel skid caused by braking too hard, you stop braking, let the wheels roll again, then countersteer
    • E. In a front wheel skid the vehicle keeps going straight no matter which way you turn the steering wheel
    Ver respuesta y explicación

    Respuesta: A. Most skids happen because the vehicle was going too fast for the conditions, D. In a drive wheel skid caused by braking too hard, you stop braking, let the wheels roll again, then countersteer, E. In a front wheel skid the vehicle keeps going straight no matter which way you turn the steering wheel

    Skids are mostly a speed problem, whether that is braking too hard, turning too fast or accelerating too hard on a slick surface. A drive wheel skid ends when the wheels start rolling again, so you release the brake or ease off the accelerator first, then steer back the other way as the rear comes into line. A front wheel skid is different, because the steering tires have already lost their grip, so the only cure is to let the vehicle slow until they bite again. Black ice is a thin clear layer and the road just looks wet, so watch your mirror arms and antenna for ice as a warning.

15. 15. Which statement about alcohol and a CDL is correct?

    • A. A CDL holder is held to the same blood alcohol limit as any other driver in the state
    • B. Coffee, fresh air or a cold shower will bring a blood alcohol level down faster
    • C. Alcohol only affects a driver once the legal limit has been passed
    • D. Driving a commercial vehicle with a blood alcohol concentration of 0.04 or higher is a violation, and any detectable alcohol puts the driver out of service
    Ver respuesta y explicación

    Respuesta: D. Driving a commercial vehicle with a blood alcohol concentration of 0.04 or higher is a violation, and any detectable alcohol puts the driver out of service

    The commercial limit of 0.04 is half the 0.08 that applies to ordinary drivers in most states, and detectable alcohol below 0.04 still gets you placed out of service for 24 hours. Drivers are also barred from drinking within four hours of going on duty. Judgment, reaction time and vision all get worse well before any legal limit is reached, and only time removes alcohol from the body, so nothing you drink or do speeds it up.

Qué entra de verdad en el test de general knowledge del CDL

Todo el que solicita una commercial driver license hace el test de general knowledge, sea cual sea la clase de vehículo que piense conducir. Es un test escrito que pone tu estado y está hecho a partir del manual del CDL de tu propio estado, que puedes descargar gratis en la agencia estatal de licencias de conducción. La mayoría de manuales estatales son versiones ligeramente editadas del modelo de AAMVA, así que el contenido es casi el mismo en todas partes. El número de preguntas y la nota de aprobado los fija el estado, no un organismo nacional. El ochenta por ciento es la nota de corte más habitual, pero el único número fiable es el que está impreso en el manual de tu estado o en la web de licencias de tu estado. Tienes que aprobar este test antes que cualquier test de endorsement y antes de poder reservar el examen práctico.

El contenido sale de unos pocos capítulos de ese manual. Conducir con seguridad es el mayor: inspección del vehículo, control básico, cambio de marchas, ver y comunicarse, gestionar el espacio y la velocidad, detectar peligros, maniobras de emergencia, control y recuperación del derrape, conducción nocturna, invernal, con calor y de montaña, pasos a nivel, procedimientos en caso de accidente e incendios. Transportar carga con seguridad añade peso, equilibrio y sujeción. Después vienen la aptitud del conductor, las normas sobre alcohol y drogas y los límites básicos de horas de servicio para conductores de mercancías, que ahora mismo son 11 horas de conducción tras 10 horas seguidas de descanso, dentro de una ventana de 14 horas. Las normas federales de horas de servicio sí se revisan, así que confírmalas con la norma vigente de la FMCSA y no con un dosier antiguo.

Lo que varía según el estado es todo lo que rodea al contenido: la tasa, cuántos intentos tienes, cuánto esperas entre repeticiones, si el test es en papel o en pantalla táctil y si hay lector disponible. Air brakes, combination vehicles, tankers, doubles and triples, passenger, school bus y hazardous materials son todos tests aparte con sus propias preguntas, así que general knowledge es el primer test escrito y no el examen escrito entero. Las normas federales de entry level driver training también se aplican desde 2022 y cambian cuándo puedes presentarte al examen práctico y al test teórico de hazmat. Consulta la página de tu estado para saber el orden actual de los pasos.

Cómo usar esta muestra

Estas 15 preguntas se quedan dentro del material de general knowledge y profundizan más de lo que lo haría una muestra mixta del CDL. Preguntan por qué existe una norma, no solo qué dice: por qué das marcha atrás hacia el lado del conductor, por qué un camión vacío puede costar más de frenar que uno cargado, por qué la marcha corta se mete antes de la pendiente y no a mitad de la bajada. Ese razonamiento es lo que te mantiene los números en la cabeza el día del examen, y es lo que te pide la carretera después. Aquí faltan a propósito las preguntas de air brakes, de acople y de placards, porque pertenecen a sus propios tests y a sus propias páginas, enlazadas abajo. Si estudias para más de un test escrito, haz esas muestras en sesiones separadas en vez de mezclarlo todo.

Hazlo de una sentada con el manual cerrado, después lee la explicación de todas las preguntas, también de las que acertaste. Trata una respuesta fallada como un capítulo que releer, no como un dato suelto que memorizar. Si fallaste la pregunta de la distancia de seguimiento y la de la distancia de frenado, el tema al que volver es la gestión del espacio en conjunto, no esos dos números. Una lista corta de números sí merece la pena aprendérsela de memoria, porque el test los pregunta directamente: las dos profundidades mínimas de dibujo del neumático, la regla de un segundo por cada 10 pies de longitud del vehículo, las tres partes de la distancia de frenado, una amarra por cada 10 pies de carga con un mínimo de dos, y el nivel de alcohol de 0,04. Casi todo lo demás lo puedes razonar.

Después lee el manual entero. Es gratis, te lo puedes leer en unas cuantas tardes y las preguntas de verdad salen de ahí. Cuando un número que hayas leído en otro sitio no coincida con el manual de tu estado, gana el manual, porque tu estado escribió el test. Esta muestra tampoco puede cubrir todo lo que puede caer. La conducción nocturna, las comprobaciones con calor, la conducción de montaña, la conducción distraída y agresiva, dónde se colocan los triángulos de emergencia cuando paras en el arcén y qué hacer en el lugar de un accidente entran en el test y ninguno está en estas 15 preguntas. Una forma rápida de encontrar esos huecos es repasar los títulos de los capítulos y marcar todos los que no sabrías resumir en una frase.

Cómo StudyPDF crea tests completos con tu propio material

Quince preguntas te enseñan dónde flojeas. Por sí solas no te preparan, y un banco de preguntas genérico no sabe qué manual estatal estás estudiando ni en qué pone más peso tu autoescuela.

StudyPDF va por otro camino, parte de tu material. Subes el manual del CDL de tu estado, los dosieres de tu autoescuela o los apuntes que tomaste en clase, y Bo, el agente de estudio, crea tests de práctica completos con esas páginas exactas. Cada pregunta sale de tu material y cada explicación señala de dónde viene la respuesta, así que puedes ir directo a la página cuando algo no te cuadre. Puedes generar tests nuevos tantas veces como quieras, centrarlos en un área como la sujeción de la carga o la gestión del espacio, y seguir qué temas sigues fallando.

No hace falta ningún documento para empezar. Si no tienes nada que subir, di solo un tema, por ejemplo la inspección de siete pasos o la recuperación del derrape, y Bo escribe un test de práctica sobre eso. Empezar es gratis.