Risk Zone: Close and Directly in Front of My Truck

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 it is concerning that some personal vehicle drivers allow themselves to sit close in front of my truck for any length of time.  They are in one of the riskiest zones.  No matter whether they have just passed me on the left or right and then pulled into my lane close in front of my truck or I have closed on them from the rear, I can only conclude they are distracted, oblivious to the danger and/or too trusting.  I hope the following advice to avoid this zone stays with you throughout your driving life.

Definitions of “Close” and “Lead Threshold”

By “close” in front of my truck I mean 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 you take.

In any situations in which you brake hard or even moderately within this risk zone, there is a possibility of a rear end collision with you.  To avoid a collision, first I have to notice your braking, and your brake lights don’t tell me the rate at which you’re slowing or stopping.  Once I’ve seen your brake lights (or noticed your slowing if your lights don’t work), I will immediately brake moderately and then hard if I see I am closing on you.  If I see you slowing drastically I will look for an “out,” a maneuver to avoid colliding with your vehicle.  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 you don’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.  Ideally you should stay well outside the lead threshold to minimize your risk.

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.  Hopefully you will comply when passing my truck.  Then once you’ve passed my truck, please, please do not slow down and settle in this risk 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.  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.


The lead threshold and collision avoidance maneuvering described above provide minimal protection from some action taken by you alone, such as slowing/stopping for a flat or blown tire, a small animal, road debris or other surface problem, or some disturbance inside your vehicle.  In a more obvious emergency happening in front of you, 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.

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.

Changing Lanes Behind You

With your vehicle at least a lead threshold ahead of me, I should be able to 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, and also any lane changes from left to right.  (Of course this assumes no drivers are alongside me.)

In emergencies requiring lane changes from both of us, I prefer to stay behind you.  I will brake hard and possibly swerve onto right shoulder or the narrow left shoulder or even into the median to try to avoid rear ending you.  Obviously the greater your lead above our threshold, the easier and safer this will be.

Preparing to Pass You

Another situation that may require encroachment into the risk zone occurs 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 behind you.  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 very risky if you pass me and then settle directly in front 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 is a very risky zone because of a truck’s size, weight and stopping distance.

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.

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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