Last Edited: July 23, 2017 // by TruckerScape, Inc.

Truck Lights and Their Functions

It has been my experience that my truck signal lights don’t get enough attention from some personal vehicle drivers occupying certain positions around my truck.  The lights on my stock truck are typical of those found on OTR (over the road) tractors towing “big box” 53 foot dry van or refrigerated trailers.  (“Stock” means the truck is not customized with extra trim lights or other accessories):

At the rear of my trailer are two pairs of red tail lights—the outside set blinks when turn signals or emergency flashers are on.  The two inside lights are brake lights.  There are also some smaller red rear clearance lights—these can be at the top corners, or along the middle of the rear top or bottom.  Clearance lights help other drivers identify my vehicle as a truck at night, in bad weather or other poor visibility conditions.  Also, at the rear bottom is a white or light yellow light illuminating the trailer’s license plate.

Along both sides of the trailer at the rear bottom corners are other red clearance lights and near the driver’s side left rear bottom corner is an amber ABS (Anti-lock Brake System) status light.  At the bottom midships (middle) point on both sides is an amber light that blinks when turn signals or emergency flashers are on.

At the front top corners of the trailer are amber clearance lights.  Refrigerated trailers have a temperature control unit on the front of the trailer with a status light on the left side that can be checked by the driver in the tractor’s large left mirror.

At the rear middle of the tractor mounted on the frame is one pair of red tail lights that blink when turn signals or emergency flashers are on.  Between the tail lights is one white backing light.  These lights are useful to me and visible and relevant to other drivers when I am bobtailing (driving without a trailer) but not when I am towing a trailer.  (A rear license plate light is provided for, but the only plate on a working truck such as mine is mounted on the front bumper.)

Mounted on the sides of the tractor in front of the doors at mid-height are amber lights that blink when turn signals or emergence flashers are on.

At the front of the tractor are headlight clusters that shine in dim or bright mode and also double as running lights when truck lights are not turned on.  At the outer edge of each headlight cluster is a small amber light that blinks when turn signals or emergency flashers are on.  Also at the front of the tractor on a visor or rim over the windshield are small amber clearance lights.

Observing and Responding to Truck Lights

One problem with my truck lights is that although they are more numerous than those on a personal vehicle, they are smaller relative to my truck’s total surface area.  In daylight certain signal lights don’t stand out strongly and some personal vehicle drivers do not observe and react to them promptly.

Drivers behind me readily recognize and react to my turn signals.  On a multi-lane road, especially on an interstate or highway, many drivers in personal vehicles speed up to get around me before I make a lane change while others hold up and wait for me and even blink their headlights to signal me to go ahead (which I appreciate and return a brief “Thank you” blink.)  I also appreciate drivers who move to a third lane when there is one, enabling me to take the second lane.  We will detail lane changes and passing in later chapters.

However, drivers behind me seem less aware and sure of what to do when my emergency flashers are on.  From behind my truck you can differentiate emergency flashers from turn signals by observing that tail lights on both sides are blinking.  When I turn on the flashers on an interstate or highway, I usually am in the process of slowing down or stopping.  I may have a problem with my truck such as a tire blowout that requires me to slow to a stop on a shoulder, or I may be slowing or stopping for some hazard in front of me such as an accident.

Since it’s difficult for you to see what’s ahead of us, it’s a good idea to slow down behind me.  If I pull over on a shoulder you can proceed past me.  If I don’t, you might choose to very carefully swing out from behind my trailer to see what’s ahead—just be sure that it is safe and lawful to do so and that you don’t interfere with oncoming traffic or cut somebody off who is behind you.

When I turn on the flashers while driving on a surface street, I may be searching for a turn or a dock.  If I stop on the shoulder or to the right on the street with flashers on, I may be trying to verify directions or even preparing to back to a dock off the street.  If I have to back up I won’t start until I am sure that traffic close behind me has cleared.

This means that I need you to very carefully swing out to the left to look at what’s ahead, and drive on past me as soon as it’s practical, safe and lawful to do so.  When stopped with traffic behind me, I may have to get out of the truck to make sure that vehicles either pass or stop far enough behind me to permit a backing maneuver if that is what is required.

In both of the above situations, I realize the inconvenience to you and just ask for your understanding and patience.

When you are alongside my truck and you see the amber side lights blinking, you can’t tell immediately if I want to change lanes or if I have the emergency flashers on for some reason because you can’t see whether the lights on the other side of the truck are also blinking.  However you can see ahead of us much more readily and whether there is a hazard that requires slowing or stopping.

If there is no hazard I appreciate your moving ahead or behind me as soon as it is practical, safe and lawful to do so to allow me to change lanes.  If you observe some hazard, you can slow down or stop.  (If no hazard but heavy traffic prevents you from moving right away I will understand.  However I may still leave signals on to let you and other drivers next to me know that I need to slow down or stop for some reason or want to change lanes as soon as we can clear the lane next to me.)

Particularly in daylight some drivers alongside my truck appear oblivious of my signal, maintaining their position instead of reacting.  They may be lost in their own thoughts or otherwise distracted or just ignoring the signal.  This is one instance in which awareness of trucks will serve you well.   One of your driving tasks is to stay observant of my side lights.

When you are towards the rear of my trailer, it should be fairly easy to spot the midships (middle) section light, even in daylight.  If you are farther forward, the midships light may not be readily visible and you will have to depend on the light on the side of my tractor.  This is a small light and in daylight the amber color tends to blend in with the white finish of my tractor, so some extra attention is required.  (Note that there are many tractors of diverse colors on the road and in daylight their side lights may be more visible.)  At night or in other dark conditions all truck signal lights are much more visible.

As we will discuss more thoroughly in the Risk Zones chapter, it is generally advisable to move out of positions alongside my truck as soon as it is practical, safe and lawful to do so.


When alongside a truck, watch for hazards ahead and be ready to help the driver avoid them (by braking hard, pulling ahead or changing lanes).

Also stay alert and ready to respond to a truck driver’s turn signals and emergency flashers.

As a general rule, move out of risk zones around a truck as soon as it is practical, safe and lawful to do so.

When you see a truck stopped ahead of you on the shoulder of a highway or on a surface street with its emergency flashers on, drive on by as soon as it is practical, safe and lawful to do so.

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