Risk Zone: Close Behind My Truck but in the Left Lane Next to Mine, Where I Can See You in My Large Left Mirror

Last Edited: May 13, 2019 // by TruckerScape, Inc.

Risk Zone Pluses and Minuses

On multi-lane highways or streets, drivers often settle in the lane to my left with the front of their personal vehicles even with, or only one or two car lengths behind the tail of my trailer.  I’m not sure of all their reasons for doing so but I believe a major one is that they can see ahead of them at a speed they are comfortable with—they don’t have to speed up to pass me.  From their point of view, it certainly beats driving directly behind my truck.  Or they may be “presenting” their vehicle to me to make sure I see it prior to passing me.  Or they may be preoccupied and not observing and acknowledging my truck’s position next to them (see the Awareness Tip in the Personal Habits Chapter).

This position keeps them out of the path of much of the debris from my truck’s tires that don’t get blocked by the mud flaps.  However in wet or snowy weather their vehicles may still be hit by water or snow thrown sideways and blown back from my trailer tandems and my truck wheels.  This may obscure their view of the road ahead and my view of them.

Whatever their reason(s), in good weather and road conditions they can see what is ahead in their lane (except on stretches of road curving to the right), but they often miss or ignore situations in which I need to move into their lane.

Changing Lanes to My Left

Obviously a lane change is required for a vehicle that has been pulled over or is being assisted by police.  The law in most if not all states requires drivers to change lanes away from roadside police activity or if that is not possible, to slow down.  Emergency vehicles and personnel and highway equipment and workers on roadsides are also afforded the same mandatory protection.  Certainly truck drivers want to swing wide to give them a safety margin.  We also change lanes for other trucks and personal vehicles stopped on the roadside, especially when those vehicles’ emergency flashers are on and/or safety triangles or flares are placed.

Another common reason that we want to change lanes is to accommodate traffic entering an interstate or highway.  Drivers merge much more easily if the first lane they reach is not occupied by a truck.

With my truck’s relatively slow cruising speed, passing even slower drivers is easier if I don’t have to delay until I can clear a vehicle (be sure of its relative position and speed) that is close behind me in the lane to my left.

You may be surprised at the limited rear distance perspective I have in my mirrors, even in my large left mirror.  Unless your vehicle’s front bumper is at least three or four car lengths behind the trail of my trailer, I can’t tell immediately and confidently whether I can safely change into your lane.  I can see my trailer’s tandems in the mirror but I can’t quickly gauge the position of my trailer tail in relation to your vehicle when you are closer.  And the last thing I want is to clip you.

Remember, I vary the position of the rear of my trailer over its tandems to properly balance the weight of the freight load I am carrying (see the Truck Length Tip in the Truck Handling Characteristics and Limitations Chapter).  So the tail extends some length back of the tandems, and I don’t necessarily see it well in my mirror, especially at night or in other low visibility conditions.  And I can’t see the spoiler at all, if my trailer has one.  So I have to perform a careful “take” on our relative positions.  And I need to ascertain your speed relative to mine to make sure you aren’t closing on me.  Where there are dashed lane lines, I may try to gauge your vehicle’s position by observing the number of dashed lane lines as they recede from where I think my trailer tail is to the front of your vehicle.

When I signal, many drivers in the left lane behind me habitually speed up to get by my truck before my lane change.  Other drivers don’t respond at all, apparently thinking that I know I won’t hit their vehicle.  A delayed “clear” process can prevent me from changing lanes in time or at all.  When I can’t change lanes in time I have to slow down, wasting time and fuel.

For routine required lane changes, you can help by remaining a good distance back of me, or by backing off if you get caught closer.  Some drivers even blink me over.  In most cases even if I slow down, there is not enough time for you to pass me before I need to swing into your lane.

In a real emergency, such as one demanding a sudden lane change to avoid a potentially fatal collision, I will not have time to clear you.  I will have to gamble that you will be able to maneuver out of my way.  This is of course the most compelling reason to stay out of this risk zone.  Ideally you would be wise to follow the one second minimum following distance guideline or even the preferable two seconds following distance guideline described in the Risk Zone:  Close and Directly Behind My Truck tip in this chapter.  Failing that, please stay at least three or four car lengths behind my trailer tail unless and until you pass me safely and lawfully.

Accidents Averted

To illustrate what can happen when you are in this risk zone, consider the following:  One evening an SUV driver in this zone prevented me from changing lanes to get around an interstate highway maintenance crew re-painting the right shoulder line.  We had passed a warning sign several miles back and traffic cones had been placed periodically along the freshly painted line.  But we were travelling at highway speed when the lights on the paint crew trucks came into sight as we rounded a curve.

The trucks were still well out in front of us when I signaled to change from the right lane to the left.  Towing a heavily loaded trailer and unable to accelerate in front of the SUV, I began to slow down to let the SUV pass me.  However, the driver also braked, staying just even with the rear of my truck and never backing off.  Unable to clear the SUV, I wound up braking to a complete stop just short of the bumper truck trailing the painting truck.  With the SUV also stopped just behind my truck, I was finally able to pull around the paint crew.  We were very fortunate that there was enough room to stop and that there was no traffic behind us.  The situation could have been much worse–I did not have to choose between taking the left lane and risking a collision with the SUV or swerving off the highway to the right.

A related incident involving my truck and two others occurred on a mountain pass descent.  I was driving in the right lane with a truck close behind my trailer’s tail in the left lane.  Rounding a curve to our left at the 65 mph speed limit, we encountered a third truck completely stopped in the right lane with its emergency flashers on but no flares, triangles or other warning devices placed behind it.  That truck was only about 200 feet in front of us, and I had just enough space to brake, signal and swerve around it in front of the truck in the left lane.

Thankfully the driver of the truck in the left lane saw the problem and allowed enough maneuvering space for me.  I was towing a lightly loaded trailer that responded well to the quick change in speed and direction.  If I hadn’t been able to avoid running into the rear of the stalled truck’s trailer, I could have been killed.  (I reported the stalled truck to the highway patrol for assistance.  The driver of that truck could been experiencing a mechanical or a medical problem and not had time or been able to put out warning devices.)

Finally, it’s important to note that the successful outcomes in both situations had been greatly aided by good weather and road conditions.


When you’re behind a truck in the lane to its left, stay at least one second of travel behind its trailer tail unless you’re going to pass.

Especially at night or in other low visibility conditions, it is difficult for a truck driver to clear your vehicle (be sure of its relative position and speed) when it is in this risk zone.

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

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