Understanding Trucker Signals

April 26, 2010 at 12:02 am 40 comments

By Chad Upton | Editor

You can’t go far on the highway without seeing a semi-truck. While they may be intimidating to some, in many cases they are the most careful drivers on the road — their life and livelihood is on the line.

Truckers usually communicate with each other using citizen’s band (CB) radios, but they communicate with you using headlights, turn signals and trailer lights. In a lot of cases, you probably don’t realize they’re doing it.

Trucks have a lot of advantages over the average driver. For example, they sit a lot higher, so they see past other cars when you can’t. Also, from their CB radio, they know about things that are around the next corner.

The most common signal is used by cars and trucks in oncoming lanes. They will double-flash their headlights when they just passed a police speed trap that you’re heading toward. While this is very helpful, be sure you know your local laws about this, in some places it is against the law.

More than two consecutive flashes from oncoming traffic signals that there is another type of danger ahead, such as a foreign object on the road and drivers should proceed with caution. These two signals are often confused, but the appropriate action is the same, slow down.

Another signal is for lane change clearance. Because semi-trucks are so long, it can be difficult for the driver to tell if he can safely change lanes in front of you. You can quickly flash your headlights when his trailer clears your car and there is room for him to move back into the driving lane (as appose to the passing lane).

This is especially useful in heavy traffic or when a truck passes you on the highway. If he has his signal on, and he has room to fit in front of you, he expects you to quickly flash your lights to give him the OK. If you do so, he will usually flash his trailer lights a number of times to say, “thank you.”

When you’re driving on the highway for a long time, you experience a condition known as velocitization — your ability to detect changes in speed is reduced. If you’re not expecting a construction zone or some other hazard that requires a sudden reduction in speed, then it can be a dangerous situation. Truck drivers will put their flashing hazard lights on when the highway traffic is coming to an abrupt stop. This signal is fairly common among drivers in Europe, but is only common among truck drivers in North America. If you understand this signal, you’ll notice it from a great distance and you won’t have to jam your brakes at the last minute.

I propose adding a “thank you” signal for motorists that move out of the passing lane when you approach from behind. Flash your left signal a couple times after your pass (or right signal if you drive on the left side of the road).

If you put in a lot of highway miles, you might consider a CB radio for earlier warnings, alternate routes and good old fashioned chit-chat. The common channel is usually 19 (although 17 is popular in some areas too). You can get a CB radio at radio shack or many truck stops.

Thanks for reading, I’m 10-7.

Broken Secrets

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Sources: Wikipedia, Velocitization

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The common channel is usually 19 (although 17 is popular in some areas too).

Entry filed under: Automotive, Demystified. Tags: , , , , , , , , , .

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40 Comments Add your own

  • 1. Damon  |  April 28, 2010 at 7:25 pm

    Good call…I knew about the double flash around here but not many of the other signals. I do live in a rural area but I couldn’t help laughing as I was heading out to the beach on a winding road I noticed a piece of ruled notebook paper on a roadside sign post. It read in a scratchy large bic-pen style font: “COP AHEAD”. Sure enough around the next corner….that poor officer didn’t have a clue.

    • 2. George  |  October 14, 2016 at 9:52 pm

      Having worked thousands of hours of radar, when I noticed traffic was slower than usual, I often found this type of sign. I did not remove the sign I just moved to another location. The whole idea is to keep traffic at a legal pace.

  • 3. Scott Taylor  |  April 30, 2010 at 12:36 am

    One common one on the autobahn – if you are hogging the left lane (the passing lane), and someone wants to get past you, they’ll put on their left blinker.

  • 4. Benjamin Shover  |  May 4, 2010 at 9:56 am

    I got my CDL a couple years ago, during the course I was told not to flash my lights like most drivers do. If something does go wrong, like you flash your lights to tell a driver that he can get over and they cause a wreck you can be held liable in some states, so I don’t do it.

    • 5. DanJ  |  February 16, 2011 at 8:39 am

      You might be confusing the definition of “flash”. “low-beams on then low-beams off then low-beams on” vs “low-beams on then high-beams on then low-beams on”. It’s illegal (in most states, I believe), to shine high-beams at another motorist in any case. It’s not illegal to blink low-beams.

  • 6. Kim  |  June 7, 2010 at 3:10 am

    My husband has been an OTR Truck Driver for over 13 years. He has told me about some of these signals. He always says that common courtesy on the roadways, (even between other truck drivers), is a thing of the past. It would be great get this secret out. Also, even though a semi’s breaks are of course, larger than a standard vehicle, they need time and distance to slow their trucks down, especially when carrying a large load. There are few things a driver can do when someone slams on the brakes in front of him or cuts him off, but to attempt to not kill anyone. Be safe out there everyone :)

    • 7. baloouriza  |  November 15, 2014 at 4:36 pm

      Depends on the region. I noticed people are much more aware of these signals here in the southern plains states (Texas, Oklahoma, Kansas) and they’re routinely used (even clearance flashing for vehicles for four-wheelers that clearly can’t see out their back window because they’re towing or trying to move with just one trip in the car). Get out west? Dead. You’re pretty much screwed if you don’t have a CB (though I used to guide truckers through Portland in the best possible lane because I knew they’d hold an even speed and if I was going the same way, could guide them through which helped me not get crowded while trying to hold an even speed in a manual).

  • 8. alex zandra  |  July 7, 2010 at 8:56 am

    Too many laws.old fashion better.b kind b considerate.b safe. b helpful.dont push ur self or others to the point of no return.take time to the job rite.simple facts of live.we all have free will.not sure if this was intended for a person or a company or just getting it off my cheast.

  • 9. Ric  |  November 18, 2010 at 8:11 am

    My driving priorities are 1. Safety, 2. Consideration, 3. The Law. I find paying attention to the first 2 satisfies the third, but it sounds like that may not be true with flashing my lights. Still, I am willing to pay the consequences when the law conflicts with safety and consideration because the law should never prevent me from doing what I know to be right.

    • 10. baloouriza  |  November 15, 2014 at 4:38 pm

      I’d definitely put the speed limit in the Safety category. Most road surfaces and structures like bridges are budgeted around that, since excessive speed causes unusual forces that wear out these surfaces faster, making a hazardous condition for future traffic (not to mention higher expenses via taxes for all of us).

  • 11. CG  |  February 16, 2011 at 1:12 am

    Flashing indicators either left-right-left or right-left-right says Thanks in the UK. You’ll usually get a headlight flash from the vehicle that you just passed in response.

    • 12. baloouriza  |  November 15, 2014 at 4:39 pm

      In the US it usually means “Shut your blinker off, you’ve had it on for the last five miles.”

  • 13. Peter Coldeman  |  February 16, 2011 at 6:30 am

    I have an 40*2 LED array mounted against the rear window of my wagon. It is normally turned off, but with a click of a switch I can set it to display some pre-programmed messages. I have THNX, FU and U DICHED.

  • 14. Lauren Friend  |  February 16, 2011 at 6:56 am

    I use the single flash to indicate to an overtaking semi that he is clear to move back across, I call the thank you (left right left blinker) the blinker dance and I get a big kick out of it when I get one.

  • 15. Anon  |  February 16, 2011 at 10:20 am

    “Thank-you” is OFF-ON (night) or ON-OFF (day.)

  • 16. bc_msg  |  February 16, 2011 at 12:59 pm

    Truck drivers are awesome. I need a “my bad” signal :)

  • 17. Driver  |  February 16, 2011 at 2:06 pm

    The warning signal saved me from a deer. Trucker had his warning signals on, concerned with him having his warning lights on, i was prepared to slow / stop from hitting it.

  • 18. Lara  |  March 9, 2011 at 12:17 am

    It depends on what kind of understanding you gain. This is how it works. You need to understand the signals.

  • 19. P.  |  March 13, 2011 at 8:29 pm

    Quick correction: this should be “as opposed to” instead of “as appose to”.

  • 20. drbillquick  |  May 4, 2012 at 9:52 am

    In the US, if someone else is hogging the passing lane, the overtaking vehicle flashes their lights at the culprit numerous times. (this sometimes works…)

  • 21. Jenny Hu  |  December 27, 2012 at 1:28 pm

    Any one can tell me what is an obey line at a weigh station?

  • 22. Earl  |  March 3, 2014 at 9:02 pm

    I’m a commercial driver and when I encounter a hazard on the road I will flash my hazard lights 3 times then the signal light of the side of the road the hazard is on 3 times. Such as if there are animals on the road ahead in my oncomming lane then I will flash hazards 3 times followed by my left turn signal 3 times then repeat.

  • 23. Murph  |  March 28, 2014 at 6:05 pm

    I need to know what signal I give to the trucker when i am in the passing lane and a trucker needs to move in that lane in front of me. Want to let him know it is ok?

    • 24. baloouriza  |  November 15, 2014 at 4:29 pm

      Vacate the passing lane. You shouldn’t be cruising in it to start with, and truckers generally move out of the passing lane to let others use it in the situation you describe.

    • 25. George  |  October 14, 2016 at 9:58 pm

      Same thing, just flash your headlights and give him room to come into your lane.

  • 26. Paul Johnson  |  November 15, 2014 at 4:28 pm

    I usually let my hazards flash a few clicks for a thank you (similar to the thank you truckers use with their trailer lights), mostly because I drive a fleet spec Chevy, and as such, the lights are automatically controlled (so I can’t just flip the taillights on and off a couple times). This seems to be understood by most people.

  • […] Copied from Trucker Safety Signals […]

  • 28. Answering Questions #TruckerTuesday - donnahup.com  |  February 23, 2016 at 6:10 am

    […] source […]

  • 29. Don Arata  |  February 28, 2016 at 11:17 pm

    From a trucker, don’t flash your headlights at night to let me know it’s ok to come in the lane. Turn your headlights off and on once quickly. Flashing your brights in my mirror is blinding!

  • […] For example, you probably already know that when a truck (or just another car) puts on their blinker to get into your lane, quickly flashing your brights at them says, “go ahead.” If they gently tap their brakes twice, that’s their way of saying, “thank you.” Broken Secrets outlines a few others: […]

  • […] For example, you probably already know that when a truck (or just another car) puts on their blinker to get into your lane, quickly flashing your brights at them says, “go ahead.” If they gently tap their brakes twice, that’s their way of saying, “thank you.” Broken Secrets outlines a few others: […]

  • […] For example, you probably already know that when a truck (or just another car) puts on their blinker to get into your lane, quickly flashing your brights at them says, “go ahead.” If they gently tap their brakes twice, that’s their way of saying, “thank you.” Broken Secrets outlines a few others: […]

  • 33. Jack  |  May 4, 2016 at 6:25 am

    If there is a law making flashing of headlights illegal if the purpose of the flashing is to communicate with another driver, then that law is likely unconstitutional.


  • 34. Pykey  |  October 4, 2016 at 8:47 pm

    I live in Australia and I remember seeing about 30 cars in a row flash their lights on our way out of town one day just to warn of a cop. In our area these signal are used all the time, good to know our truckers and even normal drivers out here are keeping up the courtesy.

  • 35. Alicia  |  November 8, 2016 at 6:20 pm

    When a trucker turns his right signal light on and there is no where’s to turn off the road, does it mean it’s safe to pass him ?

    • 36. Al  |  February 19, 2019 at 4:56 pm


  • 37. Harvey Tomsho  |  March 26, 2017 at 10:38 pm

    Need to know how to prove to the courts that this skill light was turned off we don’t have a camera on board but my passenger and I both Witness the sign the end of we were empty

  • […] Signals are there to be used. This rule implies to all participants in traffic. Truck drivers should take this very seriously as they are often unable to visualize the traffic around them good. Every action should be announced in advance by the use of a proper signal in order to avoid accidents. Sometimes it can be too late, but it is never too early to hit the brakes because prompt signaling gives everyone time to prepare. […]

  • 39. Chrissy Kupstas  |  July 23, 2021 at 2:32 am

    keep us up to date like this. Thanks for sharing.

  • 40. How Do You Signal a Truck Driver? – Big Rig Pros  |  August 30, 2021 at 12:25 pm

    […] A truck flashing its headlights into oncoming traffic signals that there is either a police cruiser or block, that traffic has stopped, or that there has been an accident up ahead. Even though you won’t know exactly what’s coming, it’s a sign to slow down and carry on with caution. How Truck Drivers Communicate […]


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