Conocimientos generales — examen de práctica 2026

IncorrectoRespuesta correcta: A — Go back to neutral, let the clutch out, bring the revs up until they suit the speed you are travelling, then make the shift again

The gear refuses because engine speed and road speed have drifted apart while you were in neutral. Reconnecting the engine in neutral and setting the rpm to match the road speed rebuilds the condition the gear needs, and then it goes in normally. Nothing is wrong with the transmission that speed matching does not fix.

Forcing the lever when a gear will not take. The obstruction is a speed mismatch inside the box, and force damages the very components that would otherwise let you have a gear again.

IncorrectoRespuesta correcta: B — Either engine speed on the tachometer or road speed on the speedometer, once you know the ranges for your vehicle

Both instruments describe the same event from different sides: the operating rpm range tells you when the engine has reached the top of its useful band, and the road speeds each gear is good for tell you the same thing in mph. Either is a valid reference once you have learned the numbers for the vehicle you drive, and engine sound becomes a useful cross-check with experience.

Looking for the one correct indicator. Drivers who rely on sound alone in an unfamiliar vehicle, or who never learn their vehicle's ranges at all, are guessing at the moment control depends on precision.

IncorrectoRespuesta correcta: A — Let the clutch begin to take up drive while the brake is still held, keeping the truck held — on the parking brake if needed — until the engine has enough power to move it

Rollback happens in the instant between the brake releasing and the engine taking the load, so the fix is to overlap the two: the clutch is already biting, or the parking brake (or a trailer hand valve, if fitted) is holding, until there is enough power to move forward. Release the holding device only after the engine is pulling.

Believing engine revs and a fast clutch release substitute for a proper overlap. Dumping the clutch on a loaded truck either stalls it or lurches it, and the vehicle still rolls back in the gap before it grabs.

IncorrectoRespuesta correcta: B — Headlights on low beam

Poor visibility runs both ways: whatever is hiding other traffic from you is hiding you from them, and marker lights alone do not lift a vehicle out of a grey background. Low-beam headlights do. High beams throw their light back at you off rain and snow, and they bother other drivers in daylight as much as at night.

Believing high beams cut through precipitation and that dazzle is only a night-time concern. Water in the air throws high-beam light straight back at you, and oncoming drivers are affected in poor daytime visibility too.

IncorrectoRespuesta correcta: B — Black ice, which is invisible from the cab because you are looking straight through it at the pavement

Black ice gives you no visual cue of its own; all you get is a surface that reads as wet. Below freezing, that wet look has no innocent explanation, and any road that looks wet in those temperatures should be treated as ice until proven otherwise.

Reading a wet-looking surface as harmless water regardless of temperature. Water and black ice look identical from the cab; the temperature is the only piece of information that tells them apart, and drivers who ignore it discover the difference through the steering wheel.

IncorrectoRespuesta correcta: C — Your speed has to be low enough that your stopping distance fits inside the distance your headlights actually show you

At night your sight distance is set by your lamps, not by the daylight geometry of the road. If you need more distance to stop than your beams reveal, you will see the hazard only after the point where stopping was still possible.

Assuming that a speed within the posted limit is automatically a safe speed after dark. This is overdriving your headlights, and in a loaded vehicle with a long stopping distance it is the classic night crash.

IncorrectoRespuesta correcta: A — A run between midnight and 6 a.m. after six hours of sleep or less, in a week where the driver has worked more than 60 hours

Each factor multiplies the others: six hours of sleep or less roughly triples crash risk, working more than 60 hours a week raises it by about 40 percent, and many heavy vehicle crashes fall between midnight and 6 a.m. when alertness bottoms out. Stacked together they describe the highest-risk trip a driver can take.

The belief that being an experienced night driver adapts you to the schedule. Body clock and sleep debt are physiological, not habits, so long-haul drivers on night runs are one of the highest-risk groups rather than an exempt one.

IncorrectoRespuesta correcta: B — Because someone you never saw still gets a moment to sound a horn or move out of the way

You cannot guarantee that a blind spot is empty, so the lane change itself should contain a margin for being wrong. Moving over gradually turns the maneuver into a warning that someone else can still react to, rather than a movement that arrives faster than they can respond.

Treating the mirror check as proof the lane is clear and the lane change as merely the execution of that decision. A slow change is the second line of defence for the vehicle the check missed.

IncorrectoRespuesta correcta: A — Start slowing well back and bleed the speed off gradually, so following drivers can read how much you are losing

A driver in a car has no way of judging how much speed a long vehicle must give up to get round a tight corner, and they close the gap faster than they expect to. Losing the speed early stretches it over enough distance for them to read and match, instead of presenting them with a near-stopped vehicle at short notice.

Assuming other drivers can judge your speed loss from the shape of the corner. They are estimating from what a car would need, which is nowhere near what you need.

IncorrectoRespuesta correcta: A — As a ceiling you do not exceed, whatever the traffic around you is doing

That number is the ceiling for the descent, and it is posted before the crest for a reason: once the vehicle is over the top, the choices about speed and gear have already been made. Read the signs alongside it that give the length and steepness of the grade too, because those tell you what you are committing to.

Treating a "safe speed" sign as a softer suggestion because it is not a standard black-and-white speed limit sign. The wording describes what the road can tolerate, and traffic moving faster does not change what your combination can tolerate.

IncorrectoRespuesta correcta: B — It buys you time to check your mirrors and either ease off or signal a lane change, so you are not forced into a sudden move if the car swings back across your path

Early recognition converts a future emergency maneuver into a present, unhurried one. Hard braking or a snap lane change in a loaded commercial vehicle is itself a crash risk, so the value of seeing the hazard is that it removes the need for the violent move.

The idea that quick reflexes substitute for early scanning. Reaction speed cannot recover the stopping distance a heavy vehicle needs, and the abrupt response often creates a second crash behind you.

IncorrectoRespuesta correcta: C — Reach out and feel exposed metal on the outside of the cab, such as a mirror housing or the antenna, for ice

Exposed metal on the outside of the cab collects ice at about the same time the road does, so it acts as a free thermometer you can reach without stopping. Spray, by contrast, tells you the surface is wet, and wet is the one thing black ice successfully imitates.

Thinking you have to test the surface with the brakes to find out whether it is slick. Deliberately breaking traction at speed in a heavy vehicle is how a driver turns a suspicion into a jackknife, and there is a harmless check available instead.

IncorrectoRespuesta correcta: A — He may come across into you, and you have nowhere to go if you need to move over

Riding beside traffic removes your escape route at the exact moment you might need one, and it puts you in a position where someone else's lane change becomes your collision.

The belief that traveling beside another vehicle is safe as long as you stay in your own lane, ignoring that safety depends on having somewhere to go when something goes wrong.

IncorrectoRespuesta correcta: B — Gravity is pulling the weight of the vehicle and its cargo downhill

On a grade, gravity is continuously feeding energy into the vehicle, and the more total weight there is the more it feeds. Nothing about closing the throttle opposes that, which is why controlling a descent is an active job rather than a matter of simply not accelerating.

Attributing runaway speed to something mechanical, a freewheeling gearbox or falling air pressure. Blaming a component invites a driver to look for a fault instead of recognizing a normal force that has to be managed on every grade, with every load.

IncorrectoRespuesta correcta: A — Complete the turn without backing, since backing could put you into a vehicle behind you

Backing puts your blind rear into traffic you cannot see and did not warn, which trades a manageable delay for a collision you would have no way to avoid.

The belief that backing up is a polite, low-risk courtesy, when in a large vehicle it moves the danger to the one area the driver cannot monitor.

IncorrectoRespuesta correcta: A — Not necessarily; a vehicle carrying its weight high can reach its rollover point at that very number

Taking a curve too fast ends one of two ways: the tires give up and the vehicle slides off the outside, or the tires hold and the vehicle tips over them. A high, heavy load reaches the tipping point before it reaches the sliding point, and it can reach it at the posted number. The posted speed is a ceiling you never exceed, not a guarantee.

Reading the posted curve speed as a promise that the curve is safe at that speed for whatever you are driving. Dry pavement makes it worse rather than better here, because good grip is exactly what allows a top-heavy vehicle to roll instead of slide.

IncorrectoRespuesta correcta: B — It is closer and larger than it appears in the glass

Curving the glass buys a wider field of view by shrinking everything in it, and a smaller image reads to the eye as a more distant one. So a vehicle that looks comfortably back in a convex mirror may be right beside your trailer, and any gap you judge from that image needs to be treated as smaller than it looks.

Taking a convex image at face value. Drivers who trust apparent distance in these mirrors pull across in front of traffic that was much nearer than the glass suggested.

IncorrectoRespuesta correcta: C — Because a steady pair of red lights reads as a vehicle travelling with traffic, and drivers have run into the back of parked vehicles for exactly that reason

A steady pair of red lights looks the same whether the vehicle is doing sixty or standing still, and an approaching driver closes the gap on the assumption that it is moving. The four-way flashers are what breaks that assumption, which is why they go on as soon as you stop.

Treating visibility as the whole problem. The driver behind can see you perfectly well; what they have wrong is your speed, and only a signal that says "stopped" corrects it.

IncorrectoRespuesta correcta: B — Come off the accelerator completely

Spinning drive wheels have already exceeded the grip available, and a spinning tire steers and holds nothing. Taking power away lets the wheels slow to the speed of the road surface and regain traction; more power only digs deeper into the skid, and braking hard adds a second loss of control.

Treating wheel spin as a power problem instead of a traction problem. On a slick surface the vehicle needs less throttle, applied more gradually, not more.

IncorrectoRespuesta correcta: B — A small car can normally stop in a shorter distance than your vehicle can

If the vehicle ahead can shed speed faster than you can, the gap closes during a hard stop even when neither driver does anything wrong, so extra space is the only protection.

The belief that the heavier vehicle always stops sooner because of its weight and larger brakes, when in practice the lighter vehicle stops in less distance.

IncorrectoRespuesta correcta: B — After the vehicle has reached the center of the intersection

Reaching the center first gives the rear wheels room to cut inside the path of the front wheels without dragging the left side of the vehicle across whatever is waiting there.

The belief that a left turn can be started as early as the gap allows, ignoring that off-tracking pulls the rear of the vehicle toward the inside corner.

IncorrectoRespuesta correcta: C — You need considerably more space than the calculated figure

The length-and-speed count assumes tires can grip; on a slippery surface the stopping distance grows well beyond that assumption, so the calculated gap becomes a minimum that must be enlarged.

The belief that slowing down by itself compensates for a slick road, when reduced traction lengthens stopping distance at every speed.

IncorrectoRespuesta correcta: A — Come off the throttle and disengage the clutch, so the wheels spin freely while the vehicle slows itself

While hydroplaning, the tires are riding on a film of water, so anything that stops them turning leaves them with no grip to recover with. Coming off the throttle and freeing the wheels lets speed bleed away until the tires can find the surface again, and it is the same move if the drive wheels start to skid.

The reflex that a vehicle out of control should be braked. On water, braking is what locks the wheels and removes the last chance of regaining steering; the wheels have to be allowed to spin freely, not stopped.

IncorrectoRespuesta correcta: B — You are one second short and should drop back before counting again

Four seconds is only the base figure for a 40-foot vehicle, and above 40 mph the requirement rises to five, so the current gap is short by a full second.

The belief that once the length count is satisfied the job is done, which hides the speed adjustment exactly where speed is doing the most damage.

IncorrectoRespuesta correcta: B — In states whose law permits them in motion, they are a good way to alert drivers closing on you

Traffic coming up behind badly misjudges the rate at which it is gaining on a slow vehicle, and flashers are what breaks that misjudgement in time. The catch is that permission to run them while moving is set state by state, so this is one point where you have to know the law where you are driving rather than one national answer.

Assuming flasher rules are uniform across the country. A driver who applies their home state's rule everywhere is either forgoing a useful warning or using a signal illegally, depending on which way they guessed.