General Knowledge: Night Operation

16 questions in the bank cover this topic. Everything below is drawn from the sources those questions cite.

Sources: 49 CFR 392.22, 49 CFR 393.9, TC 21-305-20 para 18-98, TC 21-305-20 para 18-99, TC 21-305-20 para 2-14, TC 21-305-20 para 3-70, TC 21-305-20 para 6-18, TC 21-305-20 para 6-22, TC 21-305-20 para 6-25, TC 21-305-20 para 6-28

What you need to know

392.22(b)(2)(iii) exempts business and residential districts, but the exemption falls away during the time lighted lamps are required where lighting is insufficient to make the vehicle clearly discernible at 500 feet.

The test is whether the vehicle is discernible at 500 feet.

The placement of warning devices is not required within the business or residential district of a municipality, except during the time lighted lamps are required and when street or highway lighting is insufficient to make a commercial motor vehicle clearly discernable at a distance of 500 feet to persons on the highway.

49 CFR 392.22

392.22(b)(2)(ii) requires three bidirectional reflective triangles or three lighted fusees within 10 minutes even during the period when lighted lamps are not required.

They must be placed within 10 minutes.

Except as provided in paragraph (b)(2)(iii) of this section, during the period lighted lamps are not required, three bidirectional reflective triangles or three lighted fusees shall be placed as specified in paragraph (b)(1) of this section within a time of 10 minutes.

49 CFR 392.22

Wet leaves between tire and road act like a lubricant, and braking is when you are asking the tire for the most grip.

Dry leaves are a smaller but real problem for the same reason.

Fallen leaves often make roads dangerous because tires are more likely to skid on them when an operator applies the brakes, especially if the leaves are wet.

TC 21-305-20 para 6-28

393.9(a) makes no distinction by time of day.

Stop lamps and turn signals do most of their work in daylight, and a trip that starts in daylight may not end in it. Stop and turn signals communicate in daylight too, which is why the rule is not limited to hours of darkness.

All lamps required by this subpart shall be capable of being operated at all times.

49 CFR 393.9

If you cannot stop inside the distance you can see, you are driving into a space you have not checked.

The rule turns an abstract worry into one you can test at any moment.

The basic rule for safe night driving is NEVER OUTRUN THE HEADLIGHTS. Stopping distance should always be less than sight distance.

TC 21-305-20 para 6-25

200 feet is the legal standard.

Note how modest that is: it is the floor your lights must clear, not a distance that makes any speed safe. None of the figures offered is the one the rule gives.

The law requires that headlights should allow the driver to clearly see any person on the highway for at least 200 feet ahead of their vehicle.

TC 21-305-20 para 6-25

You are 107 feet short of being able to stop inside your own light.

This is the arithmetic behind never outrunning your headlights, and at legal brake performance it still does not work at 55 mph. You are 107 feet short at 55 mph.

At 55 MPH, the stopping distance for a vehicle with brakes meeting the legal stopping distance requirements is 307 feet, or 107 feet more than the distance a driver

TC 21-305-20 para 6-25

Greatly restricted, which is why mirror adjustment matters more after dark than it does by day.

Vision to the sides and the rear is also greatly restricted at night.

TC 21-305-20 para 6-18

Dusk, because there is no longer enough natural light but not yet enough darkness for headlights to do their work.

It falls between two systems rather than being served by either.

Vision is especially difficult at dusk. There is no longer enough natural light to see clearly

TC 21-305-20 para 6-22

A poor substitute, which sets up the rule that follows: never drive faster than you can stop inside what they show you.

Headlights are a poor substitute for daylight.

TC 21-305-20 para 3-70

Headlights.

Parking lights mark a stationary vehicle, and at twilight the point is being SEEN, which is also why most states require headlights from sunset to sunrise.

At twilight, turn on the headlights, not just parking lights. Most states require that a driver use their headlights from sunset to sunrise

TC 21-305-20 para 3-70

An unlit vehicle is effectively invisible until you are close.

It is the hazard your own good practice cannot protect you from, only your scanning can.

Be aware that some other drivers may not have turned on their lights.

TC 21-305-20 para 3-70

Prepare to stop, with one exception: if stopping would skid you.

In a loaded vehicle that exception matters more than it does in a car, which is why you judge it before the light changes. In a loaded vehicle that exception has to be judged in advance.

If a light turns to yellow, prepare to stop unless braking will cause the vehicle to skid.

TC 21-305-20 para 2-14

Anticipating your green by watching their yellow.

You start moving while cross traffic is still clearing, which is exactly where the red-light runner will be.

One practice that often results in an accident is when a driver, who is stopped at a red light, watches the green light on the side of the traffic, and as soon as it turns to yellow, starts to move into the intersection

TC 21-305-20 para 2-14

Most never learn to use what they have.

That is the encouraging reading: the limiting factor is usually technique rather than eyesight.

Although the limits of night vision vary from person to person, most vehicle operators never learn to use night vision to its fullest capacity.

TC 21-305-20 para 18-99

Knowledge and practice rather than equipment.

Better lights help you be seen, but they do not change how your eye resolves a dim shape at the edge of the beam.

To increase the capability to operate at night, the vehicle operator must understand night vision principles and the use of night vision techniques for viewing at night.

TC 21-305-20 para 18-98

Check yourself

• Are warning devices required in a residential district with poor lighting at night?

• During daylight hours, what does the rule require when a CMV is stopped on the highway?

• When are fallen leaves most dangerous?

• What is required of the lamps on your vehicle?

• What is the basic rule for driving at night?

• How far ahead must your headlights let you see a person on the highway?

• What is the meaning of a 307-foot stopping distance against 200 feet of headlight?

• What is the effect on your side and rear vision at night?

• What part of the day does the manual single out as especially difficult for vision?

• How does the manual describe headlights compared to daylight?

• What should you switch on at twilight?

• What does the manual warn about other drivers at night?

• What is the manual's rule on a light turning yellow as you approach?

• What dangerous habit does the manual describe at traffic lights?

• What is the manual's rule on most drivers' night vision?

• What does improving your night driving actually require?

Answers are in the practice test for this topic.