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Can a semi stop faster than a car?


The Life-Altering Reality of Semi-Truck Stopping Distances

  • August 3, 2022
  • No Comments
  • Truck Accidents

Newton’s second law of motion states that the force of an object is equal to its mass multiplied by its acceleration. With respect to traffic accidents, this means that a heavy vehicle traveling at a fast rate of speed will be capable of hitting another vehicle with an impact serious enough to cause life-threatening personal injury to others. Semi-trucks weigh significantly more than the typical passenger vehicle. The average semi-truck can weigh upwards of 80,000 pounds when fully loaded with cargo, compared to approximately 4,000 pounds for a standard passenger car. This difference leads to vast discrepancies in braking distance between the two vehicles.

Understanding Semi-Truck Stopping Distances

Compared to a normal passenger vehicle traveling at the same speed, large trucks like semi-trucks take much longer to come to a complete stop, even in ideal conditions. The total amount of time it takes a semi-truck to make a stop depends on a number of factors, including the overall weight of the vehicle and the load it is carrying in its trailer, as well as the conditions of the roadway and if the driver had time to prepare for the stop or was forced to engage in emergency braking maneuvers due to unforeseen activity on the road.

According to the Federal Motor Carrier Safety Administration ( FMCSA ), a normal passenger vehicle traveling at 65 miles per hour will need approximately 300 feet to come to a complete stop. However, a fully loaded truck driving at that same speed will need about 600 feet to come to a complete stop. In other words, the semi-truck in this scenario will need about twice as much room in order to safely come to a complete stop when compared with the average car.

Factors That Influence the Stopping Distance of a Semi-Truck

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Many different factors can account for the variation of semi-truck stopping distances, as well as the severity of any injury that may result from an accident. For example, the reaction time of drivers can play a major role in how quickly a potential threat is responded to on the roads. For both passenger vehicles and trucks, it typically takes a driver about 1.5 seconds to register a dangerous situation and apply the brakes. This reaction time can be impeded if the driver is under the influence of drugs or alcohol or if they are otherwise distracted while behind the wheel.

The weight of the vehicle is another major factor that determines how long it will take a semi-truck to come to a complete stop. If the truck is carrying a heavy load, it will take longer to come to a stop than an empty truck. Heavier loads also cause semi-trucks to accelerate more quickly when going downhill, requiring extra braking power when needed.

Speed may seem like an obvious factor that impacts the stopping distance of semi-trucks, but it cannot be ignored. No matter the size of the vehicle in question, the faster it is going, the longer it will take to come to a complete stop.

Finally, the nature of a semi-truck’s braking system can impact its braking distance. While most passenger vehicles are equipped with hydraulic brakes which use liquid to shorten stop times, semi-trucks often have air brakes that take more time to work. When a truck driver first applies an air brake, air builds up across the length and breadth of the vehicle. When this air buildup is complete, the brakes begin to slow the truck. This braking process takes more time, which can impact how long a truck driver needs to prepare for a stop.

If you include weather and road conditions, this is another factor that can often exacerbate the already slow stopping time of a semi-truck. If the roads are wet or icy, it’s even more difficult for a trucker to safely bring the large vehicle to a full stop.

Common Examples of Accidents Involving Semi-Trucks

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The stopping distance required by semi-trucks is just one of many examples of factors that can contribute to major truck crashes. We have covered many of them in our blog recently, but let’s go over some of the major examples to be aware of. Keep in mind that some of these common causes could potentially go hand-in-hand with the stopping distance issue, creating an even more dangerous situation.

  • Blind spots contribute to accidents between commercial trucks and passenger vehicles in a number of ways. One common cause of accidents occurs when vehicles are following each other too closely, whether in front or behind a semi-truck. Semi-trucks need a much longer stretch of road in which to slow down, meaning any motor vehicle that stops abruptly in front of a semi-truck may not be able to avoid being hit from the rear. On a similar note, cars that follow too closely behind a semi may not be ready to brake at the same frequency that truck drivers do, leading to a collision.
  • Truck driver fatigue is another common cause of accidents. Fatigue can lead truck drivers to make careless mistakes including not completely assessing their blind spots for signs of danger. Truck drivers are expected to sit for prolonged periods of time, often at hours of the day that do not align with their normal sleep schedules. This can cause impaired judgment, leading to accidents that cause injury on the road.
  • Sudden lane changes constitute another common cause of accidents between semi-truck drivers and passenger vehicles. When either party commits a sudden lane change, it can cause a change reaction of reflexive maneuvers that can cause drivers to lose control of their vehicle. Truck drivers should take prolonged precautions to ensure there is not a vehicle in their blind spots before executing a lane change.
  • Finally, distracted driving can cause accidents between semi-trucks and passenger vehicles. When a truck driver is distracted by their phone or something else, it can lead to absent-minded decision-making that rarely includes due attention to the truck’s blind spots.

In all of the examples of semi-truck accidents mentioned above, the ability of the truck to come to a stop will impact the severity of the accident. For a truck driver, perhaps nothing is more stressful than having to make an emergency maneuver due to either an unexpected event on the roadway or their own negligent behavior while behind the wheel.

Assessing Negligence After an Accident

When the driver of a passenger vehicle is involved in an accident with a commercial vehicle like a semi-truck and suffers any kind of injury as a result, it can have an extremely traumatic impact. Because of that trauma and the expenses that are typically involved in these accidents, most people want answers. It’s common to want to know more about pursuing legal action in order to recover compensation for any damages incurred as a result of the accident.

To successfully recover compensation, a plaintiff and their legal team must be able to prove to the courts that the semi-truck driver was acting in a negligent manner in the events leading to the accident. For example, if the driver was not properly checking their blind spots in the moments leading to crash, this can likely be considered negligent behavior and therefore the driver and/or their company may be liable for compensating the injured victim.

Many commercial trucking companies utilize two-way dashboard cameras (i.e. dash cams) in the cabins of their semi trucks in order to increase accountability. In the case of an accident, these cameras can be used as evidence to determine whether or not the driver was being negligent. In addition, drivers of passenger vehicles may consider purchasing a dash cam of their own, especially if they frequently share the road with a high number of semi-trucks. In the event of an accident, the evidence gained from these devices can help courts quickly determine fault.

Illinois uses a doctrine of fault determination known as “modified comparative negligence.” Under this system, an injured party can only recover damages if they are less than 50% responsible for the events that ultimately lead to the accident and subsequent incursion of personal injury. If they are deemed by the court to be 50% or more at fault for the accident, then they will automatically forfeit their ability to recover compensation from the defendant for any expenses related to the incident.

Professional Legal Counsel in Chicagoland

For years, the truck accident attorneys at Palermo Law Group have been helping victims of accidents with semi-trucks in Oak Brook and throughout Chicagoland as they fight for the compensation they deserve. Contact Palermo Law Group today for a free consultation.



Mario Palermo is the Founder and Lead Attorney at Palermo Law Group in Oak Brook, Illinois. For the past 26 years, he has worked tirelessly to help injury victims and their families in their times of need. He is a seasoned authority on civil litigation, and also a member of the Million Dollar Advocates Forum, a prestigious group of trial lawyers who have won million and multi-million dollar verdicts and settlements. Mr. Palermo has been named a “Leading Lawyer” by his peers in 2015, 2016, 2017, 2018, 2019, 2020, 2021 and 2022.

Stopping Distances

With the advent of better brakes, vehicle stopping distances have reduced somewhat over the years but it has to be remembered that, no matter how good the brakes and tires, the laws of physics don’t change.

The most crucial point for any driver to remember is that if you double your speed — say from 30mph to 60mph — your braking distance does not become twice as long, it becomes four times as far.

Because there are differences between various vehicles, the following tables are for guidance only. The biggest factor in stopping distances is the speed at which a driver reacts to seeing the hazard in question. Under ordinary driving conditions, very few drivers indeed can get onto the brakes within half a second, and two-thirds of a second to a full second is more typical.2

Most frighteningly, Australian research has shown that the very people we expect to have the fastest reactions — young drivers — are particularly prone to effectively ‘freeze up’ with fear, at the sight of an unexpected hazard ahead, and their reaction time can therefore exceed two seconds.

Lastly, don’t forget that when you read the 60-0mph figures in literature for new cars, the automaker is giving you only the braking distance, not the overall stopping distance.

Stopping Distances for Dry Pavement/Road 1

(Copyright ©, Eddie Wren, and Drive and Stay Alive, Inc., 2003 onwards)

Stopping Distances for Wet Pavement/Road 1

Overall Stopping Distance Can Be:

(Copyright ©, Eddie Wren, and Drive and Stay Alive, Inc., 2003 onwards)

Remember – 1: When the road is icy or covered with compacted snow or diesel fuel has been spilled (a particular risk near certain gas stations), the ‘braking distance’ for your vehicle can be as much as ten times further than for dry roads/pavement.

Remember – 2: ……………Any fool can drive fast enough to be dangerous!

1 For non-US readers, ‘pavement’ is the American word for the road surface. We are not referring to the British meaning of the word, which is the same as the American ‘sidewalk.’

2 The ‘thinking distances’ shown allow for two-thirds of a second reaction time. This varies from one driver to another and for individuals who are ill, tired or simply not concentrating, it can be much longer.

3 The 80mph examples are not here to condone breaking any speed limits but instead to illustrate the extra dangers faced by, and caused by, those people who exceed the usual highway limits.

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Our goal is to provide drivers of all ages and in all countries with additional or updated information that can greatly enhance your safety on today’s busy roads.

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Florida CDL Handbook: Controlling Speed

With the Florida CDL Driver Handbook, you can study up on the issues that specifically relate to earning your CDL endorsement.

Florida CDL Handbook: Controlling Speed

2. Driving Safely

  • 2.1. Vehicle Inspection
  • 2.2. Basic Control of Your Vehicle
  • 2.3. Shifting Gears
  • 2.4. Seeing
  • 2.5. Communicating
  • 2.6. Controlling Speed
  • 2.7. Managing Space
  • 2.8. Seeing Hazards
  • 2.9. Distracted Driving
  • 2.10. Aggressive Drivers/Road Rage
  • 2.11. Driving at Night
  • 2.12. Driving in Fog
  • 2.13. Driving in Winter
  • 2.14. Driving in Very Hot Weather
  • 2.15. Railroad-highway Crossings
  • 2.16. Mountain Driving
  • 2.17. Driving Emergencies
  • 2.18. Antilock Braking Systems (ABS)
  • 2.19. Skid Control and Recovery
  • 2.20. Accident Procedures
  • 2.21. Fires
  • 2.22. Alcohol, Other Drugs, and Driving
  • 2.23. Staying Alert and Fit to Drive
  • 2.24. Hazardous Materials Rules For All Commercial Drivers

Driving too fast is a major cause of fatal crashes. You must adjust your speed depending on driving conditions. These include traction, curves, visibility, traffic and hills.

2.6.1 — Stopping Distance

Figure 2-11

Perception Distance + Reaction Distance + Braking Distance =Total Braking Distance

Perception Distance. This is the distance your vehicle travels from the time your eyes see a hazard until your brain recognizes it. The perception time for an alert driver is about 3/4 second. At 55 mph, you travel 60 feet in 3/4 second or about 81 feet per second.

Reaction Distance. The distance traveled from the time your brain tells your foot to move from the accelerator until your foot is actually pushing the brake pedal. The average driver has a reaction time of 3/4 second. This accounts for an additional 60 feet traveled at 55 mph.

Braking Distance. The distance it takes to stop once the brakes are put on. At 55 mph on dry pavement with good brakes, it can take a heavy vehicle about 390 feet to stop. It takes about 4 1/2 seconds.

Total Braking Distance. At 55 mph, it will take about six seconds to stop and your vehicle will travel about 450 feet.

The faster you drive, the greater the impact or striking power of your vehicle. When you double your speed from 20 to 40 mph the impact is 4 times greater. The braking distance is also 4 times longer. Triple the speed from 20 to 60 mph and the impact and braking distance is 9 times greater. At 60 mph, your stopping distance is greater than the length of a football field. Increase the speed to 80 mph and the impact and braking distance are 16 times greater than at 20 mph. High speeds greatly increase the severity of crashes and stopping distances. By slowing down, you can reduce braking distance.. See Figure 2.11

The Effect of Vehicle Weight on Stopping Distance. The heavier the vehicle, the more work the brakes must do to stop it, and the more heat they absorb. But the brakes, tires, springs, and shock absorbers on heavy vehicles are designed to work best when the vehicle is fully loaded. Empty trucks require greater stopping distances because an empty vehicle has less traction.

2.6.2 — Matching Speed to the Road Surface

You can’t steer or brake a vehicle unless you have traction. Traction is friction between the tires and the road. There are some road conditions that reduce traction and call for lower speeds.

Slippery Surfaces. It will take longer to stop, and it will be harder to turn without skidding, when the road is slippery. Wet roads can double stopping distance. You must drive slower to be able to stop in the same distance as on a dry road. Reduce speed by about one-third (e.g., slow from 55 to about 35 mph) on a wet road. On packed snow, reduce speed by a half, or more. If the surface is icy, reduce speed to a crawl and stop driving as soon as you can safely do so.

Identifying Slippery Surfaces. Sometimes it’s hard to know if the road is slippery. Here are some signs of slippery roads:

  • Shaded Areas. Shady parts of the road will remain icy and slippery long after open areas have melted.
  • Bridges. When the temperature drops, bridges will freeze before the road will. Be especially careful when the temperature is close to 32 degrees Fahrenheit.
  • Melting Ice. Slight melting will make ice wet. Wet ice is much more slippery than ice that is not wet.
  • Black Ice. Black ice is a thin layer that is clear enough that you can see the road underneath it. It makes the road look wet. Any time the temperature is below freezing and the road looks wet, watch out for black ice.
  • Vehicle Icing. An easy way to check for ice is to open the window and feel the front of the mirror, mirror support, or antenna. If there’s ice on these, the road surface is probably starting to ice up.
  • Just After Rain Begins. Right after it starts to rain, the water mixes with oil left on the road by vehicles. This makes the road very slippery. If the rain continues, it will wash the oil away.
  • Hydroplaning. In some weather, water or slush collects on the road. When this happens, your vehicle can hydroplane. It’s like water skiing—the tires lose their contact with the road and have little or no traction. You may not be able to steer or brake. You can regain control by releasing the accelerator and pushing in the clutch. This will slow your vehicle and let the wheels turn freely. If the vehicle is hydroplaning, do not use the brakes to slow down. If the drive wheels start to skid, push in the clutch to let them turn freely.

It does not take a lot of water to cause hydroplaning. Hydroplaning can occur at speeds as low as 30 mph if there is a lot of water. Hydroplaning is more likely if tire pressure is low, or the tread is worn. (The grooves in a tire carry away the water; if they aren’t deep, they don’t work well.)

Road surfaces where water can collect can create conditions that cause a vehicle to hydroplane. Watch for clear reflections, tire splashes, and raindrops on the road. These are indications of standing water.

2.6.3 — Speed and Curves

Drivers must adjust their speed for curves in the road. If you take a curve too fast, two things can happen. The tires can lose their traction and continue straight ahead, so you skid off the road. Or, the tires may keep their traction and the vehicle rolls over. Tests have shown that trucks with a high center of gravity can roll over at the posted speed limit for a curve.

Slow to a safe speed before you enter a curve. Braking in a curve is dangerous because it is easier to lock the wheels and cause a skid. Slow down as needed. Don’t ever exceed the posted speed limit for the curve. Be in a gear that will let you accelerate slightly in the curve. This will help you keep control.

2.6.4 — Speed and Distance Ahead

You should always be able to stop within the distance you can see ahead. Fog, rain, or other conditions may require that you slow down to be able to stop in the distance you can see. At night, you can’t see as far with low beams as you can with high beams. When you must use low beams, slow down.

2.6.5 — Speed and Traffic Flow

When you’re driving in heavy traffic, the safest speed is the speed of other vehicles. Vehicles going the same direction at the same speed are not likely to run into one another. In many states, speed limits are lower for trucks and buses than for cars. It can vary as much as 15 mph. Use extra caution when you change lanes or pass on these roadways. Drive at the speed of the traffic, if you can without going at an illegal or unsafe speed. Keep a safe following distance.

The main reason drivers exceed speed limits is to save time. But, anyone trying to drive faster than the speed of traffic will not be able to save much time. The risks involved are not worth it. If you go faster than the speed of other traffic, you’ll have to keep passing other vehicles. This increases the chance of a crash, and it is more tiring. Fatigue increases the chance of a crash. Going with the flow of traffic is safer and easier.

2.6.6 — Speed on Downgrades

Your vehicle’s speed will increase on downgrades because of gravity. Your most important objective is to select and maintain a speed that is not too fast for the:

  • Total weight of the vehicle and cargo.
  • Length of the grade.
  • Steepness of the grade.
  • Road conditions.
  • Weather.

If a speed limit is posted, or there is a sign indicating «Maximum Safe Speed,» never exceed the speed shown. Also, look for and heed warning signs indicating the length and steepness of the grade. You must use the braking effect of the engine as the principal way of controlling your speed on downgrades. The braking effect of the engine is greatest when it is near the governed rpms and the transmission is in the lower gears. Save your brakes so you will be able to slow or stop as required by road and traffic conditions. Shift your transmission to a low gear before starting down the grade and use the proper braking techniques. Please read carefully the section on going down long, steep downgrades safely in «Mountain Driving.»

2.6.7 — Roadway Work Zones

Speeding traffic is the number one cause of injury and death in roadway work zones. Observe the posted speed limits at all times when approaching and driving through a work zone. Watch your speedometer, and don’t allow your speed to creep up as you drive through long sections of road construction. Decrease your speed for adverse weather or road conditions. Decrease your speed even further when a worker is close to the roadway.

Subsections 2.4, 2.5, and 2.6
Test Your Knowledge

  1. How far ahead does the manual say you should look?
  2. What are two main things to look for ahead?
  3. What’s your most important way to see the sides and rear of your vehicle?
  4. What does «communicating» mean in safe driving?
  5. Where should your reflectors be placed when stopped on a divided highway?
  6. What three things add up to total stopping distance?
  7. If you go twice as fast, will your stopping distance increase by two or four times?
  8. Empty trucks have the best braking. True or False?
  9. What is hydroplaning?
  10. What is «black ice»?

These questions may be on the test. If you can’t answer them all, re-read subsections 2.4, 2.5, and 2.6.

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