How Long Does It Take an 18-Wheeler to Stop?

Braking is a key element of avoiding any accident. For 18-wheelers, semis, and other large trucks, braking on time is especially important. Large trucks can weigh as much as 80,000 pounds, making them about 26 times heavier than the average passenger vehicle. Because of their immense weight, semi-trucks and 18-wheelers require a much longer amount of time to stop compared to smaller vehicles, like cars and pickup trucks.

According to the National Highway Traffic Safety Administration (NHTSA), large trucks were involved in nearly 5,500 traffic fatalities and more than 153,000 traffic-related injuries in 2023. Though the overall number of large truck accidents nationwide decreased between 2022 and 2023, the fact remains that semis, big rigs, and 18-wheelers continue to present significant danger to others on the road.

One way to prevent these devastating events is to ensure that truck drivers are properly trained in critical safe driving techniques, such as leaving enough space between themselves and the vehicles they are following. It’s also important that braking systems are routinely inspected and maintained. By taking such measures, trucking companies and other responsible parties can help improve the safety of our shared roads.

How Much Longer Does a Semi-Truck Take to Stop Compared to a Car?

The two most important factors that determine stoppage time are vehicle weight and speed. The average passenger vehicle is approximately 3,000-4,000 pounds (with occupants). For a 4,000-pound car traveling at 65 mph, it takes 316 feet to stop. An 80,000-pound 18-wheeler traveling at the same speed would take 525 feet to stop. That’s nearly double the amount of stoppage time.

And this is just the amount of time it would take an 18-wheeler to stop in ideal conditions. If it’s raining or the road is icy, the amount of time it will take any vehicle to come to a complete stop can change dramatically.

Factors Affecting the Stopping Distances of a Semi-Truck

The weight and quality of a truck’s brakes aren’t the only factors that influence how long it takes to stop it.

There are three things that factor into how long it takes to stop a truck:

• Perception Distance: Perception distance is how far a truck travels as a driver notices a situation that requires them to slow down or stop their vehicle. This length can vary based on how alert a driver is, the conditions on the road, and any other factors that can impact a driver’s reactions, such as the influence of alcohol or drugs.
• Reaction Time: Reaction time is how long it takes the driver to react to a situation. As with perception distance, reaction time also depends on the individual, including how alert they are, as well as external factors, such as weather conditions, traffic patterns, and whether the driver is under the influence of alcohol or drugs.
• Braking Distance: The braking distance is how long it takes the truck to physically stop after the driver applies the brakes.

It’s important to consider all three stopping distance factors because they can significantly impact how long it takes an 18-wheeler to stop. While the example above mentions that it takes about 525 feet to stop a truck, this figure only includes the braking distance of the truck based on its speed and weight. Perception distance and reaction time can significantly impact stopping distance. If the driver is not paying attention or has a slow reaction time, it can take hundreds of feet more to stop.

What Is Semi-Truck Brake Lag?

Semi-trucks have another factor that influences stopping time: brake lag. Most passenger vehicles use hydraulic brake systems, but 18-wheelers usually have air brakes. While hydraulic brakes begin to function as soon as the brake pedal is depressed, air brakes have a lag between when they’re activated and when they actually work.

When a truck driver applies brakes, air needs to build up throughout the system before the brakes activate. While this usually takes just 4/10 of a second, when combined with other factors—such as reaction time and the overall weight of the truck—brake lag can significantly impact stopping time.

Brake Maintenance Is Crucial for Accident Prevention

Because trucks have much longer stopping distances than smaller, passenger vehicles, and because any wear and tear can greatly affect braking time and effectiveness, it is incredibly important that 18-wheelers receive adequate brake maintenance. Even if it is only a matter of feet, well-maintained brakes allow truck drivers to accurately anticipate the required stop distances for their vehicles, which keeps other motorists safe.

Trucking companies must ensure that their fleets are kept in good condition. This includes adequately maintaining truck brake systems to meet federal and state regulations. Failure to do so constitutes negligence and can serve as the basis for liability after a truck accident.

What Is a Regular Performance-Based Brake Test (PBBT)?

Faulty brake systems are among the leading causes of truck accidents. Most people assume that a defective brake system translates to a catastrophic failure of a vital component. However, what many do not realize is that faulty brakes are not always the result of defective manufacturing. In truth, most brake issues are caused by improper or inadequate maintenance.

Improper brake maintenance can lead to the following:

• Brake imbalance
• Thinning brake pads
• Brakes permeated by grease
• Worn out brakes due to worn out tires

For this reason, commercial vehicle maintenance must include regular performance-based brake tests (PBBT). A PBBT quantitatively assesses the braking performance of a vehicle, directly measuring the amount of force the brake applies at each wheel and axle, as well as the force applied to the vehicle as a whole.

These tests also assess a truck's overall braking capability through stopping performance tests, which are designed to determine what a vehicle's stopping distance is under different conditions. Regular PBBTs are conducted with specialized equipment which detects most brake problems. Truck companies should perform these tests in addition to truck lot brake-performance evaluations.

Brake Safety Week

Every year, the Commercial Vehicle Safety Alliance (CVSA) conducts a week-long safety campaign known as Brake Safety Week in which local, state, provincial, territorial, and federal motor carrier safety officials throughout the United States, Mexico, and Canada perform roadside inspections to find commercial trucks with brake system violations or brakes that are not adjusted correctly. Since the program began, the CVSA has inspected over 3.8 million brake systems.

In 2024, more than 16,700 inspections were conducted on commercial vehicles throughout North America. On Brake Safety Day, a total of 4,898 inspections were conducted on a single day. On that day, certified inspectors found 570 commercial vehicles in violation of critical brake-related inspection items. This accounted for 11.6% of all commercial vehicles inspected that day.

Although Brake Safety Week and Brake Safety Day cannot cover every single commercial vehicle driven in North America, it is a start. Initiatives like these help drive home the importance of brake maintenance and motivate trucking companies to remain in compliance with federal and state regulations.

Hurt Because of a Collision Caused by Unsafe Braking? Call Our Team.

While trucks are harder to stop than normal vehicles, it’s up to trucking companies to make sure their drivers are adequately trained in operating within the safe limits of their vehicles. When a driver fails to stop in time and collides with other vehicles, it’s often because they weren’t allowing enough distance to safely stop or were traveling too fast for current road or weather conditions.

Additionally, if a truck driver or trucking company does not routinely conduct appropriate maintenance on a vehicle's braking system, and that vehicle is involved in a severe accident, both the driver and the company may be held liable for injuries they cause other motorists. If you or a loved one was injured in a trucking accident, it is imperative that you speak with an attorney. Faulty brakes may be involved, and time is of the essence in a truck accident investigation.

If you’ve suffered because of a preventable truck accident, call Arnold & Itkin today. Our truck accident lawyers have secured billions of dollars in settlements and verdicts on behalf of drivers. We fight for the answers people deserve after serious accidents and demand the compensation they need to rebuild. No matter what.

Your consultation with our truck accident law firm is free when you call (888) 493-1629.