You are driving on the highway and overtaking a large truck. As soon as you pass it, you suddenly see a brief flash of light in your mirror . You might immediately think the driver is angry. Or that you are driving too slowly and need to move to the right quickly. However, such a brief light signal after overtaking usually means something completely different. Often, the truck driver is actually trying to help you.
Truck drivers use various informal signals on the road. They can send each other short messages using their headlights and turn signals. A single short flash of light after an overtaking maneuver often has a very practical meaning. Below, you can read exactly what that signal entails and why truck drivers do this.
Why truck drivers do this
A truck with a semi-trailer can be well over sixteen meters long. This sometimes makes it difficult to see exactly where the rear of the truck ends from the cab. This plays an important role, especially during overtaking. Moreover, trucks often drive at approximately the same speed. As a result, the speed difference during an overtaking maneuver is sometimes only a few kilometers per hour. Consequently, a truck can drive alongside another truck for quite a long time.
The driver being overtaken often has a clear view of the end of the other combination. As soon as the entire semi-trailer has passed, he can briefly signal with his headlights. This indicates that there is sufficient room to move back to the right. Such a signal is therefore usually intended in a friendly manner. The truck driver is not trying to rush his colleague; he is simply helping him to better estimate the length of his vehicle.
Motorists can also get such a flash.
The signal is primarily used between truck drivers. However, you may also encounter it as a car driver. This happens, for example, when you are traveling with a caravan or trailer. With just a passenger car, you can usually clearly see when you have passed a truck. With a caravan behind the car, that is much more difficult. Your vehicle combination is suddenly several meters longer.
A truck driver may therefore also briefly signal to you with his headlights. By doing so, he lets you know that not only your car, but also your caravan, has passed him. This occurs regularly on busy German motorways, for example. However, this does not mean that you must immediately steer to the right. Always check your own mirrors first. You alone remain responsible for a safe lane change.
Sometimes a thank you follows.
Anyone paying close attention may see something else happen after the light signal. Truck drivers regularly thank each other for this help. For example, a driver who has moved back to the right might briefly use their hazard lights. Sometimes, the left and right turn signals are also used for just a moment. By doing so, the driver is essentially simply saying: thank you.
It is a kind of informal language among road users . There are various types of these signals. However, they are not all officially defined and can differ from country to country. Therefore, if you see such a signal, you must always assess the situation. After all, a flash of light can mean something else at other times.
It is not official permission
Although many truck drivers understand these signals, they are not official traffic rules. In the Netherlands, according to traffic regulations, flashing and audible signals primarily serve a function in the event of imminent danger. Therefore, legally, a brief flash of light does not mean you are granted permission to change lanes. Nor does it give you the right of way. At most, the driver behind you can indicate that he sees sufficient space.
That difference is important. Therefore, always keep looking yourself before moving to the right. Check your mirrors and maintain sufficient distance from the truck . Also, do not drive directly in front of the truck. Heavy vehicles require much more distance to come to a stop. Extra space between your car and the truck is therefore always wise.
Not every flash of light means the same thing.
If you see a truck flashing behind you, pay close attention to the moment it happens. Does the flash occur exactly after you have overtaken the truck? Then there is a good chance the driver is trying to help you. If the signal occurs at a different time, something else might be going on. Perhaps the driver wants to warn of danger. It could also mean that another traffic situation requires his attention.
That is why you can never rely blindly on a single light signal. View it primarily as additional information from another road user. Ultimately, you must always judge for yourself whether a maneuver is safe. So, the next time a truck briefly flashes its lights after overtaking, you don’t need to panic immediately. Chances are there isn’t an irritated driver behind you at all. He is probably just trying to tell you that you have completely passed him. A small gesture, but one that can make driving behind long vehicle combinations a lot easier.
