Idaho CDL — General Knowledge: Speed & Space Management Practice Test

Question 1

You are pulling a trailer and make a quick lane change. What does the manual warn can happen?

Accepted Answer

The trailer can be flipped by the crack-the-whip effect — Trucks with trailers are subject to crack-the-whip, in which a fast lane change is magnified toward the rear. The manual notes there are many accidents where the trailer alone has gone over.

Answer

The tractor's brakes release

Answer

The fifth wheel unlocks

Answer

The trailer's ABS switches off

Question 2

How may the stopping distance of an empty tank vehicle compare with that of a full one?

Accepted Answer

The empty tank may take longer to stop — The tank section reminds drivers that a tanker running empty can need more distance to stop than a loaded one, and that wet roads double normal stopping distance.

Answer

The empty tank always stops shorter

Answer

The empty tank cannot be stopped with the foot brake

Answer

They always stop in the same distance

Question 3

Why is it so easy to lock up the wheels of a lightly loaded combination vehicle?

Accepted Answer

With little weight aboard, its strong brakes and stiff springs leave the tires with poor traction — Large combinations actually take longer to stop empty than full. Springs and brakes sized for a full load leave a light rig with little traction, so the wheels lock readily and the trailer can swing out or the tractor jackknife.

Answer

Its tires are overinflated

Answer

Its trailer has no brakes when empty

Answer

Its engine brake is switched off

Question 4

When you pull trailers at night, how does the combination section say to set your speed?

Accepted Answer

Slowly enough that your headlights show an obstacle while you can still change lanes or stop without a sudden move — Sudden steering can tip a trailer, so at night the speed has to be low enough that anything in the road shows up in the headlights with room left for a gentle lane change or stop.

Answer

Ten mph over the daytime speed, to clear traffic

Answer

Match the fastest traffic

Answer

Whatever the posted truck limit is, regardless of visibility

Question 5

Why do doubles and triples skid and lose traction more readily when conditions turn bad?

Accepted Answer

The drive axles must pull a longer rig with more dead axles — In poor weather, on slick roads and in the mountains, a multi-trailer rig is longer and has more unpowered axles for the drive axles to drag along, so skids and lost traction are more likely.

Answer

Their tires are narrower

Answer

They have fewer brakes than a single trailer

Answer

Their engines are governed lower

Question 6

How does cargo loaded off to one side of a trailer affect rollover risk?

Accepted Answer

It makes the trailer lean, so a rollover is more likely — A load that sits to one side tilts the trailer and raises the chance of going over. The manual says to center the cargo and spread it out as far as you can.

Answer

It has no effect

Answer

It lowers the center of gravity

Answer

It only affects braking

Question 7

In a rig pulling more than one trailer, which wheels off-track the most in a turn?

Accepted Answer

The last trailer's rear wheels — Longer vehicles off-track more. The powered unit's rear wheels off-track some, a trailer's rear wheels more, and with several trailers the final trailer's rear wheels cut inside the farthest.

Answer

The tractor's drive wheels

Answer

The tractor's steering wheels

Answer

The front wheels of the first trailer

Question 8

When inspecting a sliding fifth wheel, why check that it isn't set too far forward?

Accepted Answer

In turns the tractor frame could hit the landing gear, or the cab could hit the trailer — A slider positioned too far forward takes away turning clearance. The check is that the tractor's frame won't strike the landing gear, and the cab won't strike the trailer, when the rig turns.

Answer

The kingpin will unlock

Answer

The air lines will be too short

Answer

The trailer brakes won't release

Question 9

What does excessive heat do to brake drums that adds to brake fade?

Accepted Answer

It expands them, so the shoes and linings must move farther and press with less force — Overheating changes the lining chemically, which cuts friction, and it makes the drums grow. Expanded drums are farther from the shoes, so the shoes travel more and push against the drum less firmly.

Answer

It shrinks them, so the shoes drag

Answer

It polishes them, so they grip better

Answer

It cracks the wheel studs

Question 10

As a school bus approaches a railroad crossing, what does the recommended procedure have the driver do about speed and brakes?

Accepted Answer

Slow down, downshift if the bus has a manual transmission, and try the brakes — The approach steps begin with reducing speed, which in a manual-transmission bus includes dropping to a lower gear, and checking that the brakes work. The hazard lights go on about 200 feet before the crossing.

Answer

Hold speed and cover the brake

Answer

Speed up to clear the crossing quickly

Answer

Shift to neutral and coast

Question 11

How far can the blind spot behind a school bus extend, according to the mirror section?

Accepted Answer

50 to 150 feet, or as much as 400 feet on a longer, wider bus — The outside flat mirrors leave a blind spot directly behind the rear bumper. It normally runs 50 to 150 feet and, on a long and wide bus, may reach 400 feet.

Answer

5 to 10 feet, never more

Answer

Exactly one bus length

Answer

A quarter mile

Question 12

With air brakes, an average driver traveling 55 mph with good traction and good brakes needs a total stopping distance of more than how many feet?

Accepted Answer

450 feet — Brake lag adds about 32 feet at 55 mph, bringing the total for an air-braked vehicle to more than 450 feet, compared with the 419 feet given for the general case.

Answer

419 feet

Answer

216 feet

Answer

319 feet

Idaho CDL — General Knowledge: Speed & Space Management practice test

Study questions with answers

1. You are pulling a trailer and make a quick lane change. What does the manual warn can happen?

2. How may the stopping distance of an empty tank vehicle compare with that of a full one?

3. Why is it so easy to lock up the wheels of a lightly loaded combination vehicle?

4. When you pull trailers at night, how does the combination section say to set your speed?

5. Why do doubles and triples skid and lose traction more readily when conditions turn bad?

6. How does cargo loaded off to one side of a trailer affect rollover risk?

7. In a rig pulling more than one trailer, which wheels off-track the most in a turn?

8. When inspecting a sliding fifth wheel, why check that it isn't set too far forward?

9. What does excessive heat do to brake drums that adds to brake fade?

10. As a school bus approaches a railroad crossing, what does the recommended procedure have the driver do about speed and brakes?

11. How far can the blind spot behind a school bus extend, according to the mirror section?

12. With air brakes, an average driver traveling 55 mph with good traction and good brakes needs a total stopping distance of more than how many feet?

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