What Is the Stopping Distance of a Semi-Truck?

Many Indiana drivers understand the fact that the size and weight of large commercial trucks add to the impact and the amount of damage a truck can do in a collision with a passenger vehicle. The truck weight of a loaded 18-wheeler or similar “big rig” means that a semi-truck driver needs a much greater distance to come to a stop to avoid a truck accident.

The Federal Motor Carrier Safety Administration (FMCSA), the agency that regulates interstate trucking, considers long stopping distances to be one of the top three safety challenges for large trucks and buses.

The FMCSA says a fully loaded truck traveling under good conditions at highway speeds requires a distance of nearly 200 yards—almost two football fields— to stop. That’s much more than the distance required of smaller passenger vehicles.

When a tractor-trailer follows too closely or is speeding, it’s easy to see the potential danger the large truck poses.

Truck Stopping Distance vs. Car Stopping Distance

To avoid accidents, commercial trucks and tractor-trailers need greater distance and time to come to a complete stop. Truck drivers have to be aware of this, especially if driving at high speeds.

Under ideal conditions, the FMCSA calculates the stopping distance of semi-trucks vs. cars as follows:

• A normal passenger vehicle traveling at a speed of 65 miles per hour would take about 316 feet to stop.
• For a fully-loaded commercial truck, the stopping distance of it running at 65 miles per hour is about 525 feet.

A truck’s stopping distance increases, even more, when it is hauling a heavy load and/or there are adverse road conditions like snow, ice or rain.

Trucks typically weigh 20 to 30 times more than passenger vehicles, with a truck weighing up to 40 tons (80,000 pounds) and a typical passenger vehicle at 2 tons (4,000 pounds). This affects a truck’s acceleration, handling and braking. A truck’s weight also makes it accelerate more quickly going downhill.

How Large Truck Brake Systems are Different

There are basically three elements to “total stopping distance”:

• Perception Distance – The distance a vehicle travels as the driver identifies the need to slow down or stop to avoid a hazard.
• Reaction Time – The time it takes for the driver to act upon the decision to slow down once he or she has recognized the need.
• Braking Distance – The distance a vehicle travels from the time a semi-truck driver begins pressing on the brake pedal until the vehicle comes to a stop.

A fourth factor that applies to trucks is “brake lag.” Brakes on semi-trucks are not like brakes on regular passenger vehicles. Most passenger vehicles on the road have hydraulic brakes, which are liquid and faster. Semi-trucks have air brakes, which have a lag time.

You’ve probably heard the whooshing sound of air escaping a large truck’s brake system as it came to a stop beside you at a light. When a trucker first applies brakes, the air has to build up and spread the length and breadth of the truck before the brakes can actually begin to slow the vehicle. This adds to stopping time and distance.

A truck’s “service brakes” are used during normal driving.

A seque­nce of events occurs when a trucker pushes the brake pedal:

1. Air moves into a brake chamber through airlines.
2. The air forces out a pushrod.
3. The pushrod pushes the slack adjuster.
4. The camshaft turns.
5. The turning of the camshaft twists the S-Cam.
6. The brake linings are forced to contact the brake drum.

If the brake drum overheats, it will expand away from the brake shoes. Then the drum and shoes won’t make complete contact. The other brakes must work harder to compensate. If the situation continues too long, other parts of the system will also overheat and fade, leading to brake failure.

In 2009, the National Highway Traffic Safety Administration (NHTSA) issued long-awaited new braking standards requiring a tractor-trailer traveling at 60 miles per hour to come to a complete stop in 250 feet, versus the old standard of 355 feet – a reduction of truck stopping distance of roughly 30 percent.

Under the rule, a small number of very heavy tractor-trailers are required to stop at 310 feet when running at 60 mph. In addition, the rule requires that all heavy fully loaded tractor-trailers stop within 235 feet when loaded to their lightly loaded vehicle weight.

When the NHTSA adopted the rule, it estimated that the new braking requirement would save 227 lives and prevent 300 serious injuries annually, while reducing property damage costs by over $169 million a year.

In 2015, NHTSA began the years-long process of rulemaking to require forward collision warning and automatic braking capability on trucks with a gross vehicle weight rating of 10,000 pounds or more. While this technology is significantly reducing rear-end crashes in passenger vehicles in the U.S., most commercial trucks sold here don’t have front-crash prevention.

How to Avoid a Truck Accident

An Indiana defensive driving instructor suggests using caution when driving near large trucks and staying away from fast-moving trucks on open roadways when possible.

You should give a truck extra space and stopping distance whenever possible, and you should always leave an escape option on the road.

Other tips for avoiding a collision with a large truck include:

• Don’t cut in front of large trucks, because they take longer to come to a complete stop.
• Allow a safety cushion. Keep a safe following distance between you and a truck ahead of you. Look a quarter-mile down the road and keep up with upcoming exits. Truckers often cause accidents by making unexpected lane changes to exit the highway.
• Stay out of blind spots. If you can’t see the truck driver in his or her side mirrors, then the truck driver cannot see you and could make a lane change into your vehicle.
• Use caution when driving near tractor-trailers.

Is the Truck Driver to Blame for Brake Failure That Led to an Accident?

Even when automated braking and collision warning systems become a requirement for America’s long-haul trucking fleets, truck drivers will still be responsible for operating their vehicles safely on public roads to avoid accidents.

Trucking companies will continue to be responsible for ensuring brakes are maintained and operating properly when their vehicles are on the road.

When truckers or truck owners act negligently and cause truck crashes, innocent drivers or others who have been injured have a right to seek compensation for their losses.

If you have been injured in a truck accident in Indiana, you should discuss your legal options to pursue an injury claim with a knowledgeable truck accident attorney. At Craig, Kelley & Faultless LLC, our attorneys represent people injured in truck crashes and handle cases on a contingency-fee-basis. We only get paid if we obtain an insurance settlement or jury award for our client. Contact us now in Indianapolis or Batesville, IN, for a free discussion of your case.