Risk Zone: Close in Front of My Truck and in the Left Lane Next to Mine

Last Edited: April 16, 2017 // by TruckerScape, Inc.

When You Have Passed Me

When passing my truck on the left or even the right on the open road (typically on interstates or major highways with two or more lanes in each direction, in sparse traffic, usually in the countryside), most personal vehicle drivers move through the risk zones and leave me behind briskly.

But a few drivers pass me and then wind up close to the front of my truck in the left lane next to mine.  They may settle only 2 or 3 car lengths out in front of me.  Even if there is no traffic in front of us, they may stay in this position for some time.  Then they finally pull away, or if they have slowed up I may have to pass them on the right.  Their behavior indicates they may be distracted and/or believe they are not in any danger.

While not as serious as settling close and directly in front of my truck, this zone is riskier than it may appear, as the following information indicates.

 Definitions of “Close” and “Lead Threshold”

First we need to define “close.”  For reasons that will become apparent soon, we will use the same definition as in the Risk Zone:  Close and Directly in Front of My Truck tip.  “Close” means any distance less than the distance my truck is traveling in 2 seconds.  For example if my truck and your vehicle were traveling at 60 mph (miles per hour) the “close” distance (risk zone) in front of my truck would be anything less than 180 feet (rounded up) or approximately 12 compact-size 14 1/2-foot car lengths or approximately 2 1/2 big rig truck lengths.  This lead threshold is arbitrary, not government-mandated.  It is my way of estimating a minimal time window for me to recognize and respond to any sudden action taken by a personal vehicle driver in front of me.

In any situations in which a personal vehicle driver close in front of my truck brakes hard or even moderately, there is a possibility of a rear end collision.  To avoid a collision, first I have to notice the vehicle braking, and the vehicle’s brake lights don’t tell me the rate at which it is slowing or stopping.  Once I’ve seen the vehicle’s brake lights (or noticed it slowing if the lights don’t work), I will immediately brake moderately and then hard if I see I am closing on it.  If I see the vehicle slowing drastically I will look for an “out,” a maneuver to avoid colliding with it.  That generally means a lane change or steering onto a highway shoulder.

Now imagine this process happening at 60 mph within 2 to 4 seconds (I have somewhat longer than the 2 second lead threshold assuming the vehicle in front of me doesn’t stop instantly).  This is not enough time for me to do a lot, considering it takes about 1/10 of a mile (500 feet) to stop my fully loaded truck from 60 mph in good road and weather conditions and much less distance to stop your personal vehicle.  So I think we should treat this 2 second lead threshold as our practical basic minimum on the open road at highway speeds.  Anything less definitely increases your risk, whether you are directly in front of my truck or in the left lane next to mine.  Ideally you should stay well outside the lead threshold to minimize your risk.

Examples of Hazardous Situations

You may wonder why you need to be so far away if you are not directly in front of me.  Suppose we are on a typical interstate with two lanes in each direction and with your vehicle close in front in the left lane and my truck in the right lane.  Also suppose there is traffic in both lanes in front of us but it is outside our respective lead thresholds.  I am still not able to safely make routine lane changes to the left to bypass situations such as emergency vehicles or highway maintenance equipment and personnel or other vehicles and people on the right shoulder, because such changes put you in a more dangerous zone (see the Risk Zone:  Close and Directly in Front of My Truck tip).  Instead I may slow down and cheat to the left without changing lanes, then resume my cruising speed (this burns extra fuel).  If there is a serious problem on the right shoulder, I will brake and switch to the left lane, hoping you don’t brake in front of me.

Suppose there is an emergency in the traffic ahead or some other hazard requiring quick action, and you brake but stay in your lane.  I have the options of not braking or braking and staying in the right lane, or braking and swerving onto the right shoulder.  In this situation I have three possible “outs.”  However, if you have to brake even moderately and swerve into my lane, you will be so close in front of me that I’m likely to have to brake hard and swerve onto the right shoulder to avoid rear ending you.  My only out is the right shoulder which may or may not be free of obstacles such as overpass supports and debris.

Suppose there are two or three vehicles inside the lead threshold in front of my truck (shame on them) but none in front of you.  If an emergency in the right lane and/or right shoulder requires a quick move to the left, you complicate the move for me and the vehicles in front of me.  Hopefully you maintain your speed forward.  Then the vehicles in front of me may be able to brake and swerve left behind you, with my truck behind them.  There is still the possibility of a rear end collision.

Suppose there are other vehicles in the left lane behind you and alongside my truck, but none inside the threshold in front of my truck.  If you are settled close to me (not pulling away from me) there is a good possibility that drivers behind you will want to pass.  They will pull close to your rear, pushing you to let them by on your left or right.  If you don’t speed up but move to the right lane directly in front of me, you have entered a more dangerous zone (see the Risk Zone:  Close and Directly in Front of My Truck tip).  If you don’t speed up and stay in the left lane, some drivers will aggressively try to squeeze between my truck and your vehicle and pass you on your right.  In that case I may be forced to slow down to let you get farther ahead and make more room for them, then resume my cruising speed (this burns extra fuel).

NOTE:  Many times I’ve seen truck drivers pull close, within 1 or 2 car lengths, to the rear of slower personal vehicles traveling in the left lane on the open road, to “strongly request” their drivers to move right and let the trucks pass.  If you get caught with a truck directly behind and crowding you and my truck close behind in the lane to your right, you should recognize that you are definitely in a high risk zone.  You should move right as soon as safe and lawful to do so.  Then with the same urgency you should exit the high risk zone in front of my truck.  I will be watching in case I have to slow down for you.  (Again, see the Risk Zone:  Close and Directly in Front of My Truck tip.)

Many states post road signs illustrating how a vehicle passing another on the left is required to leave a safe distance in front of the passed vehicle before moving into its lane.  While you’re not violating this law when you’ve passed my truck on the left and then remain close in the left lane, you can still create hazardous situations with other vehicles around us.

After you’ve passed my truck, please, please do not slow down and settle in this zone!  Depending on other traffic around us I will wait momentarily for you to pull away and if you don’t, I will slow down to let you get farther ahead and then resume my cruising speed (this burns extra fuel) or I will prepare to pass you on the right.  Preferably you will pull much farther away from my truck as soon as it’s safe and lawful to do so.  This is a very important component of defensive driving:  It will make both of us safer.  You will have to pay less attention to my truck behind you and I will be able to pay less attention to your vehicle and more attention to other factors around my truck.

There are situations similar to those described above on multiple-lane highways (sections of interstates and other major highways with more than two lanes in each direction).  All of these situations become safer if you move well outside the lead threshold.


The lead threshold and collision avoidance maneuvering described above provide minimal protection from some action taken by you or a personal vehicle driver in front of us, such as slowing/stopping for a flat or blown tire, a small animal, road debris or other surface problem, or some disturbance inside the vehicle.  In a more obvious emergency happening in front of us, there is a good possibility that I will have seen it (from my higher vantage point) and will have begun braking hard and preparing for evasive action simultaneously with you or perhaps earlier than you.

But the lead threshold is not always practical in light of current automobile performance and driver behavior in good weather and road conditions.  For example the threshold is not easy to maintain in heavier traffic such as on multiple-lane city freeways.  In those situations it is generally safer for me and other truck drivers to “go with the flow” at or close to traffic speed than to slow down significantly.  Whether I’m in the right lane or in one of the lanes to the left, some drivers in passenger vehicles will still pass me on the left or right and then fill the space on my left, right or directly in front.  In such conditions I am doing well if I can maintain a truck length (approximately 5 compact-size car lengths) of space in front of me across the 3 lanes, though I will constantly try to extend it.

Passing You

While safer to pass on the left, especially on the open road, I may pass you on the right if your speed is slower than mine and you do not move right as I draw close to you.

If you do move right for me, another situation requiring encroachment into the risk zone may occur.   This can happen when I am preparing to pass you on your left, and I am travelling only slightly faster than you (5 mph or less) and there is other traffic behind me.  I may need to pull closer to you, while signaling for a lane change and letting faster vehicles close behind pass me first.  Then when my truck is within about one truck length of your rear, I will change to the lane left of you.  This is to try to prevent other personal vehicle drivers behind me from dangerously passing me on the right and then squeezing left ahead of me before I get alongside your vehicle.

When you see me in the lane to your left and about to overtake you, I hope you will not speed up.  Doing so leaves me hanging in that lane, vulnerable to impatient drivers pulling up behind you on my right and blocking me from aborting the pass and returning to the right lane.  You might be surprised how many drivers in personal vehicles do speed up, if only slightly.  Perhaps as they see me closing on them they think they have let their speed drop off and need to restore it, or they just don’t want to wind up behind my truck. Whatever the reasons, they put me in a bind.

I don’t mind you speeding up as I get closer, so long as you do it before I encroach into your lead threshold and begin the passing maneuver.  I would just as soon not have to pass you.  With my truck governed at 65 mph, on the open road it is easier to cruise in the right lane and let all the faster drivers pass by on my left.

Driving on Grades

The lead threshold is obviously less critical going up an extended grade such as ascending a mountain pass where my truck’s stopping distance will be reduced.  In most cases you should be able to pull well ahead of my truck and beyond your lead threshold (see the Passing Me Basics tip).

Frequently on extended grades, an interstate or highway with two lanes in both directions is expanded to three or more uphill lanes.  This is where drivers in faster personal vehicles can help trucks by staying left in the passing lane(s) as much as possible.  This allows truck drivers going uphill to use a middle lane and the right lane so faster trucks can pass slower trucks and the occasional slower personal vehicle on the left.  By staying left and beyond the lead thresholds of trucks in the right lane(s), you facilitate safety and help truck drivers conserve fuel (see the Passing Me on Grades tip).

On steep downhill grades such as mountain pass descents, signs restrict truck drivers to the right lane(s) and require them to control their speeds by downshifting and using engine brakes and/or service brakes.  Personal vehicle drivers can help trucks on highways with three or more descent lanes where trucks are permitted to use the right two lanes.  Drivers in heavier trucks gear down more than those with lighter loads.  Leaving the right two lanes free whenever possible allows drivers with lighter loads to pass the slower trucks and still descend safely and lawfully with less fuel burned.  Though all drivers are in lower gears and using engine brakes and/or service brakes, you should still stay well beyond the lead thresholds.

On less steep downhill grades trucks may be permitted to travel at highway speeds.  Descending these however, is risky if you pass me and then settle in the left lane within the lead threshold.  Some drivers seem to forget how much more difficult it is to control and slow/stop my truck suddenly from highway speed downhill.  Your lead threshold should be extended significantly, preferably to 1/10 of a mile (500 feet) or more if possible.


This zone is risky because of potentially hazardous situations you cause with other vehicles around your vehicle and a truck.

Allow a safe lead distance before returning to the lane of a truck or any other vehicle you have passed.

Whenever possible maintain at least 2 seconds of travel (lead threshold) in front of a truck and extend your lead on downhill grades, even if you stay in the lane to its left.

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.

When a truck trailing your vehicle moves into the lane to your left to pass you, let the driver complete the pass and return to your lane in front of you.

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