7CDLFree CDL permit study for every state
Content preview, before public launch
Course › General Knowledge

Communicating: signals, being seen and warning triangles

General Knowledge4 minManual section 2.5

Other drivers cannot know what you will do until you tell them, and they may not notice you even in plain sight. “Communicating” means signaling your intentions and making your presence known. This lesson also covers where to place warning devices when you stop.

Signal your intentions (2.5.1): turns and lane changes

Three good rules for turn signals:

  • Signal early. Turn the signal on well ahead of the turn; this is the best way to stop other drivers from trying to pass you.
  • Signal continuously. You need both hands on the wheel to turn safely, so leave the signal on — do not cancel it until the turn is complete.
  • Cancel your signal after the turn (if your signals do not cancel themselves).

Lane changes: turn the signal on before you change lanes. Change lanes slowly and smoothly, so a driver you did not see has a chance to honk or get out of your way.

Signal when you slow down

When you know you will have to slow down, warn the drivers behind you: tap the brake pedal lightly a few times so the brake lights flash. Use the four-way emergency flashers when you are driving very slowly or are stopped.

Warn others in these situations:

  • Trouble ahead. Your big vehicle may block their view of a hazard. Flash your brake lights to warn them.
  • Tight turns. Most car drivers do not know how slowly a big vehicle must go for a tight turn. Brake early and slow down gradually.
  • Stopping on the road. Trucks and buses sometimes stop in the road to unload cargo or passengers, or at a railroad crossing. Flash your brake lights. Do not stop suddenly.
  • Driving slowly. Drivers often do not notice how fast they are closing on a slow vehicle until they are very close. If you must drive slowly, turn on your emergency flashers if it is legal — flasher laws differ from state to state.

Don't direct traffic; communicate your presence (2.5.2)

Do not direct traffic. Do not wave or signal to other drivers that it is safe to pass. You could cause a crash, be blamed for it, and it could cost you many thousands of dollars.

When passing a vehicle, pedestrian or bicyclist, assume they do not see you — they could move in front of you. Where it is legal, give a light tap on the horn; at night you can switch from low beams to high beams and back. Still, drive so that you would not hit them even if they never notice you.

When it is hard to see — dawn, dusk, rain or snow — if you have trouble seeing others, they have trouble seeing you. Turn on your headlights, not just identification or clearance lights. Use low beams; high beams bother people in daytime as well as at night.

When parked at the side of the road, turn on the four-way flashers, especially at night. Do not trust the taillights — drivers have hit parked vehicles thinking they were moving normally.

Use your horn when needed. It lets others know you are there and can prevent a crash. But it can startle others and be dangerous if used when not needed.

Emergency warning devices when stopped

If you must stop on a road or the shoulder of any road, put out your emergency warning devices (reflective triangles) within 10 minutes.

  • One-way or divided highway: place them 10 feet, 100 feet and 200 feet behind the vehicle, toward the approaching traffic.
  • Two-lane road with two-way traffic, or undivided highway: one within 10 feet of the front or rear corner (to mark the vehicle), one 100 feet behind and one 100 feet ahead, on the shoulder or in the lane where you stopped.
  • Hill, curve or other obstruction: if drivers cannot see your vehicle within 500 feet, move the rear-most triangle back down the road (beyond the hill or curve) so they get a warning.

When you carry and place the triangles, hold them between yourself and the oncoming traffic, so drivers see the triangle (and you).

Check your state

Laws on using four-way flashers while driving slowly differ by state. Check the manual of each state where you drive.

References and scope

The topic reference is listed below. Sources support verification; the lesson itself is here. The current content needs technical and language review before public launch.

Manual reference: 2.5

Official CDL handbook · Utah ↗StatesOur editorial approach

Put it into practice

Educational questions with explanations. The answer review also works without the interactive quiz.

Preparing your questions…

Review questions with answers

  1. Which is one of the three good rules for using turn signals?
    1. Signal only when cars are behind you
    2. Signal early, well before you turn
    3. Cancel the signal halfway through the turn
    4. Signal only at night
    Show answer
    Signal early, well before you turn

    Signal early, signal continuously, and cancel after the turn.

  2. Why should you keep signaling continuously during a turn?
    1. It is required only in cities
    2. It saves the battery
    3. You need both hands on the wheel to turn safely
    4. It makes the turn faster
    Show answer
    You need both hands on the wheel to turn safely

    Leave the signal on until the turn is done; you need both hands to steer.

  3. How should you change lanes?
    1. Signal first, then change lanes slowly and smoothly
    2. Change quickly so you are not in the way
    3. Change first, then signal
    4. Flash your high beams and change
    Show answer
    Signal first, then change lanes slowly and smoothly

    Changing slowly gives a driver you did not see time to honk or move.

  4. How should you warn drivers behind you that you are about to slow down?
    1. Turn on your high beams
    2. Sound your horn
    3. Wave your arm out the window
    4. Tap the brake pedal lightly a few times to flash the brake lights
    Show answer
    Tap the brake pedal lightly a few times to flash the brake lights

    A few light taps flash the brake lights and warn following drivers.

  5. When should you use your four-way emergency flashers while on the road?
    1. Whenever it rains
    2. When you are driving very slowly or are stopped
    3. When passing another vehicle
    4. Whenever you change lanes
    Show answer
    When you are driving very slowly or are stopped

    Use four-way flashers when driving very slowly or stopped (where legal).

  6. Another driver is waiting to pass you, and you can see the road is clear. What should you do?
    1. Wave them past
    2. Flash your lights to say it is safe
    3. Do not signal them; let them decide
    4. Turn on your left signal
    Show answer
    Do not signal them; let them decide

    Do not direct traffic. You could cause a crash and be blamed.

  7. You must stop on the road at a railroad crossing. How should you warn following drivers?
    1. Flash your brake lights and avoid stopping suddenly
    2. Stop suddenly so they notice
    3. Sound your horn continuously
    4. Turn on your high beams
    Show answer
    Flash your brake lights and avoid stopping suddenly

    Flash your brake lights early and do not stop suddenly.

  8. When you are about to pass a bicyclist, you should assume:
    1. They see you
    2. They will stay still
    3. They will speed up
    4. They do not see you and may move in front of you
    Show answer
    They do not see you and may move in front of you

    Always assume the person does not see you.

  9. At dawn, dusk, or in rain or snow, you should:
    1. Use only clearance lights
    2. Turn on your low-beam headlights
    3. Use high beams
    4. Use the four-way flashers while moving
    Show answer
    Turn on your low-beam headlights

    Use headlights (low beams), not only identification or clearance lights.

  10. If you stop on a road or its shoulder, you must put out emergency warning devices within:
    1. 1 minute
    2. 30 minutes
    3. 10 minutes
    4. 1 hour
    Show answer
    10 minutes

    Warning devices must be placed within 10 minutes.

  11. Where should you place warning triangles when stopped on a divided highway?
    1. 10, 100 and 200 feet toward approaching traffic
    2. 50, 100 and 150 feet behind
    3. One in front and one behind, 100 feet each
    4. 10 feet behind only
    Show answer
    10, 100 and 200 feet toward approaching traffic

    On a one-way or divided highway: 10, 100 and 200 feet toward oncoming traffic.

  12. On a two-lane, two-way road, where do you place the warning devices?
    1. All three behind the vehicle at 10, 100 and 200 feet
    2. Two in front and one behind at 50 feet
    3. Only one, 500 feet behind
    4. Within 10 feet of a corner, 100 feet behind, and 100 feet ahead
    Show answer
    Within 10 feet of a corner, 100 feet behind, and 100 feet ahead

    On two-way or undivided roads, mark the corner and place one 100 feet behind and one 100 feet ahead.

  13. You stop just past a hill crest. Drivers cannot see your vehicle within 500 feet. What should you do with the rear-most triangle?
    1. Leave it at 100 feet
    2. Move it back down the road beyond the hill so drivers are warned
    3. Put it on top of your cab
    4. Skip it and use flashers only
    Show answer
    Move it back down the road beyond the hill so drivers are warned

    If a hill or curve blocks the view within 500 feet, move the rear triangle back far enough to give warning.

  14. When walking to place warning triangles, how should you carry them?
    1. Behind your back
    2. Under your arm, pointed down
    3. Between yourself and the oncoming traffic
    4. Above your head
    Show answer
    Between yourself and the oncoming traffic

    Holding them between you and traffic lets drivers see the triangle and you.

  15. When parked at the side of the road at night, you should:
    1. Turn on your four-way flashers and not rely on taillights
    2. Rely on your taillights
    3. Leave your high beams on
    4. Turn off all lights to save the battery
    Show answer
    Turn on your four-way flashers and not rely on taillights

    Drivers have hit parked vehicles thinking they were moving; use the flashers.

  16. Using your horn when it is not needed is always safe.
    1. True
    2. False
    Show answer
    False

    False. The horn can startle others and be dangerous if used unnecessarily.

  17. Car drivers behind you may not know how slowly a large vehicle must go for a tight turn. What should you do?
    1. Stop suddenly so they notice you
    2. Brake early and slow down gradually
    3. Speed up, then turn quickly
    4. Wave them around you
    Show answer
    Brake early and slow down gradually

    Give following drivers warning by braking early and slowing gradually.

  18. At night, where it is legal, how can you let a vehicle or bicyclist you are about to pass know you are there?
    1. Turn on your interior light
    2. Turn off your headlights for a moment
    3. Flash your lights from low to high beam and back
    4. Turn on your four-way flashers
    Show answer
    Flash your lights from low to high beam and back

    When legal, tap the horn lightly or, at night, switch from low to high beam and back. Still drive so you avoid a crash even if they do not notice.