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  • Writer's pictureBrad Keating

How Long Does it Take to Stop a Fully Loaded Semi-Truck?

Updated: Nov 4, 2020

It's critical that a driver knows how long it's going to take to stop a fully loaded truck before they ever step foot inside of it. Stopping a truck of that size is nothing like smaller vehicles. Even the slightest difference in weight or speed can result in a staggering change in stopping distance.

They need to know about a few critical stopping distances, but more important than knowing the numbers is having a good reaction time. Drivers have to keep their wits about them while driving; otherwise, they risk causing severe damage and injury to other road users.

We're going to go over some essential bits of information that drivers need to know about stopping their truck in this article and some other information about the same topic. There is a short bulleted FAQ section at the end that serves as a summary to what we are about to discuss, so for those here looking for one specific piece of information, consider scrolling down to have a look at that.

How Long Does it Take to Stop a Fully-Loaded 18 Wheeler

How Long Does it Take to Stop a Loaded 18 Wheeler?

18 wheeler related crashes can have some truly horrifying results, which is partially why commercial drivers are held to such rigorous standards.

At a bare minimum, it takes 40% percent longer for a tractor-trailer to come to a complete stop when compared to the average car. Again, that's the bare minimum. This discrepancy can be far wider depending on the brake system that the semi-trucks are supporting, the road conditions, and the driver's reaction time.

For a truck driving at 60 mph on dry pavement, the stopping distance is around 335 feet. To put that into perspective, that's a little over the length of a football field. This doesn't even account for if the semi-trucks have air brakes, which increases the distance, or if the driver has a short reaction time.

As a general rule of thumb, the faster the truck is going, and the heavier it is, the longer it takes for it to come to a complete stop.

What is the Following Distance for Truck Drivers

With that knowledge in mind, it's essential to know what following distance drivers should be adhering to on the road. By maintaining the correct distance from the vehicle in front of them, the risk of a fatal collision decreases dramatically. It also gives them a better chance of stopping the truck before any crash happens, at all.

At a bare minimum, there should be an eight-second distance between them as a truck driver, and the vehicle that they are following. As with how long it takes to stop a truck, that is a bare minimum number. They can, and absolutely should, add to that number depending on the conditions at any given time.

If the road is wet or icy, they should even be considering doubling that number. Remember, it's better to be overly cautious than reckless. By not maintaining a proper following distance, they could cost someone their life.

How do Drivers Calculate Following Distance?

At a glance, it can be near impossible to tell how many seconds a driver is lagging behind the car in front of them. It's a measure of time, not actual distance, so they need to do a little bit of work to determine how far behind they are.

It's relatively simple. They need to watch the car in front of them pass some static object next to the road. This can be a sign, a tree, a pole, or anything in between. When the car they’re watching passes the item, they begin counting. They continue counting until they pass the same thing themselves.

This is the following distance that the driver is currently maintaining. This distance can change throughout their drive, but generally only by a few fractions of a second. If they check the space every once in a while, they should leave themselves plenty of time to jam on the breaks in the event of an emergency.

Other Truck Driving Space Management Tips

As well as maintaining distance when driving, there are other situations where drivers have to adhere to space management, too. For example, if they’re at a stop such as a traffic light, railway crossing, stop sign, or anything else, they should maintain at least 20 feet between them and the vehicle in front of them.

This isn't so much for safety as it is to allow them to get around the vehicle in question if it breaks down or otherwise becomes disabled. Making their presence known to other motorists can be just as important as maintaining proper distances. To assist drivers with this, turn the headlights on a half an hour before dusk, and leave them on for a half an hour after sunrise.

Also, drivers should try to use their turn signals plenty in advance. 100 feet is a good number to use. They need to make sure that they leave the signal on as they turn and don't turn them off until they are lined up straight in the lane they are now using.

Does a Loaded Truck Stop Faster?

The effect that weight has on a truck's stopping distance is a bit of a mixed bag. Logically, the more weight that is put onto a truck, the more work the breaks have to do to stop it, and the more heat that the brakes absorb.

This would lead one to think that loaded trucks take longer to stop than empty ones, but I'm afraid that's not right. The breaks, springs, shock absorbers, and tires on heavy load trucks are specifically designed to work better when the vehicle is loaded.

This means that empty trucks take longer to stop than loaded trucks, and require a greater stopping distance. There is less traction with an empty vehicle. One can end up bouncing and locking up their wheels, which results in much poorer breaking times.

How Important is a Truck Driver's Reaction Time

The reaction time of a truck driver can be critical and make all the difference between the loss and preservation of life. Some drivers might not think that a second or two would matter all that much, but in reality, every single fraction of a second counts.

The average driver has a reaction speed of 3/4 of a second, to one second. If someone is driving at 55 MPH, this accounts for 61 additional feet. That number grows exponentially as they increase in speed.

As should be obvious, when it comes to a driver’s reaction speed, we're not dealing in second; we're dealing in milliseconds. That's why it's vital that they maintain proper vigilance on the road.

What they need to understand about this, though, is that reaction time is how long it takes them to hit the breaks once they recognize a hazard. A lot of people don't consider perception time, which is how long it takes a driver’s brain to recognize the danger in the first place.

A driver's perception distance can change drastically on a day to day basis. There are certain mental and physical conditions that can affect it, as well as the speed they are traveling and the weather outside. That's not even to mention the nature of the hazard itself, which can also have an impact.

On average, an alert driver has a perception time that is 1 3/4 seconds long. At 55 MPH, this translates to 142 feet. Fewer alert drivers have longer times, which in turn translates to a much higher distance traveled.

Therefore, to put all of this into perspective, an alert driver that is driving on a dry road on a good day travels 203 feet before the breaks are even pressed.

The Effects of Speed on Stopping Distance

When discussing the effects of speed on the stopping distance of a truck, it's essential to understand that it is not proportional. If a driver doubles their speed, that does not mean that their stopping distance is double.

In general, the effects of a speed increase are four times more impactful on stopping distance. So if they double their speed, then it can take four times as long to come to a complete stop.

On top of that, the truck is also going to have four times the destructive power if they do crash. So by slowing down a little on the road, not only do they give themselves a better chance at stopping before an accident, but it means that if they do crash, it's less likely to result in fatality.

Gas Mileage of a Semi-Truck

How Many Miles Can a Driver Get Out of a Semi-Truck?

The engineering that goes into getting trucks up and running is incredibly impressive. We are talking about monster level parts that offer a ludicrous amount of performance.

This means that one generally gets a lot of miles out of one before they need to put it to rest. On average, a driver can expect to push upwards of 750,000 miles. However, it's not uncommon for a truck to reach well past one million. This is upwards of five times as many miles as the average car.

A semi-truck typically travels 45,000 miles per year, although that number can obviously differ. This means that it can take 15-16 years for a truck to be put out of commission.

What is the Gas Mileage of a Truck?

Given the size and stature of the truck, drivers generally expect to see a terrible MPG number here. However, they might not be expecting just how bad the gas mileage is.

The average MPG tends to be right around the 6.5 mark and hovers between four and eight depending on the truck. This is just for driving on flat surfaces, too. If it’s driving the truck uphill, that number can go as low as 2.9 MPG.

This makes up a large portion of the cost that goes into running and maintaining a trucking business.

The Difference Between Air Brakes and Hydraulic Brakes

While hydraulic brakes are the industry norm for smaller vehicles, most larger trucks run an air brake system. It's unlikely that a person is ever going to be driving a truck that uses hydraulic brakes, but knowing about the two different types can still be useful.

A hydraulic brake utilizes a liquid to apply force to objects. In a car, the liquid medium that is used is brake fluid. This fluid is drawn into the master cylinder from its reservoir. It is then pushed out against the brake lines when the pedal is pushed.

Hydraulic brakes are popular in smaller vehicles for two reasons. First, the relatively light construction means that the liquid is more than capable of stopping the wheels from moving. Second, a hydraulic system uses a lot less room than an air one, and as such, can fit comfortably into the frame of a smaller car.

Air braking systems are primarily used in much larger and heavier vehicles. Locomotives, large trucks, buses, and other large units are dependent on the system for braking power.

While the mechanical setup of an air brake is similar to a hydraulic one, the reason for the difference is the amount of force needed to stop the vehicle. A heavy-duty unit needs something significantly stronger than breaking fluid to bring the vehicle to a complete stop.

To ensure that the stopping power that a truck needs is always there, this brake system works in reverse to standard brakes. In other words, the brake is always engaged. Powerful springs push the mechanisms into place, holding them there until enough air pressure is available to disengage them. This pressure keeps the mechanism away from the wheels, allowing the vehicle to move.

This means that when a driver presses the brake pedal, the system releases the trapped air, and the spring pushes the mechanism back into a stopping position. Once the driver takes their foot off the pedal, that pressure begins to build again.

Not only do air brakes provide more power than hydraulics, but it is also an inherently safer system. Due to the fact that the breaks are always engaged, a failure in the system results in the vehicle coming to a stop and being unable to move. If there is a failure in a hydraulic system, the opposite is true, and the vehicle isn't going to be able to use the brakes at all.

How Long Does it Take to Stop with Heavy Braking if Travelling at 65 MPH?

On average, the stopping distances of a truck that is traveling on dry ground at 65 MPH is anywhere between 335 to 400 feet. This number changes with the weight of the truck.

A truck with an 80,000 pounds load isn't going to stop at the same distance as an empty truck. In fact, the loaded truck should stop quicker. This means that a driver needs to take their cargo into consideration when thinking about their stop distance, too.

The road conditions also play a part. Obviously, drivers need a lot more room to stop if it's wet outside. Likewise, they should consider doubling the distance that they are planning to maintain.

Truck drivers are held to a high standard because of how dangerous a large truck crash can be, so remember that due diligence can be the difference between saving and ending a life.


  • Which stops quicker: a fully-loaded large truck or an empty one?

An empty one.

  • At 60 MPH, how far is a large truck going to travel before coming to a stop?

A little over the length of a football field, or around 335 feet.

  • How should I take road conditions into account?

If the road is wet and slippery/icy, double the stop distances.

  • What kind of brakes do semi-trucks use?

Most large vehicles use air brakes because it is, overall, easier on other systems connected to the brakes.

  • Is a truck crash the responsibility of the truck driver?

It's situational, but morally yes, legally no. If a driver crashes while contracted, then their company is the one legally at fault. If the truck driver is subcontracted, though, then they can be sued.

  • How does one calculate the braking distance of their tractor-trailer ruck?

Watch the car in front of them, pass a static object like a tree. Start counting once it passes it, and stop once they pass it. That number is their braking distance.

  • What is a reasonable braking distance to have?

Depending on road conditions, a driver should have seven to eight seconds for dry pavement, and double that for wet.

  • How far can a truck driver travel before pressing on the brakes?

It depends on the reactions and perceptions of the truck driver. However, an average estimate is 203 feet before the brakes are pressed in response to a hazard.

  • Does the braking distance of a tractor-trailer increase with speed?

Yes, the braking distance of a fully-loaded tractor-trailer increases at a rate of 4x as it moves up in speed. So if one doubles their speed, they need four times the distance.

Whether you are interested in what the average semi-truck accident settlement is or the average 18-wheeler accident settlement, The Keating Firm LTD. can help get you the information you are looking for.

Disclaimer: The details included in this blog is offered for educational purposes only, and should not be taken as lawful guidance in any way. No recipients of material from this blog, clients or otherwise, should or should not act on the basis of any material consisted in the blog without seeking the appropriate legal or other professional guidance on the particular facts and situations at issue from an attorney accredited in the recipient's state.

1 Comment

Jul 26, 2023

The stopping distance of a fully loaded semi-truck depends on various factors, including the truck's weight, speed, road conditions, and the braking system's efficiency. On average, it takes a fully loaded semi real trucking traveling at highway speeds about 300 to 400 feet (approximately 91 to 122 meters) to come to a complete stop under normal driving conditions.

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