When driving a 50 foot truck at 40 mph What is the minimum following distance?

Following too closely may be defined as, “situations in which one vehicle is following another vehicle so closely that even if the following driver is attentive to the actions of the vehicle ahead he/she could not avoid a collision in the circumstance when the driver in front brakes suddenly."14

In addition to providing enough stopping time, proper following distance allows for more time to make good, well-planned decisions and affords other drivers the opportunity to scan the sides, look far enough ahead, and view the vehicle immediately in front.

The Large Truck Crash Causation Study (LTCCS) reported that 5 percent of truck crashes occurred when the Commercial Motor Vehicle (CMV) driver was following the lead vehicle too closely.15

Below are some tips that will help you maintain the correct following distance during various driving conditions.

TIP #1: Maintain a Safe Following Distance

Large trucks need additional space between vehicles to allow for safe braking and unexpected actions. In crashes, large trucks most often hit the vehicle in front of them.16

Did You Know? If you are driving below 40 mph, you should leave at least one second for every 10 feet of vehicle length. For a typical tractor-trailer, this results in 4 seconds between you and the leading vehicle. For speeds over 40 mph, you should leave one additional second.16

Did You Know? On October 15, 2007, as cars began to slow for construction in the left lane, a CMV driver failed to brake and crashed into the vehicle ahead of him, killing a 47-year-old woman. The crash also involved two other vehicles and shut down the roadway for 5 hours. The CMV driver was charged with misconduct with a motor vehicle, and following too closely.77

An example of a driver following too closely is shown in the video clip below. Training exercise questions follow the video clip.

VIDEO DESCRIPTION: The CMV driver is traveling in the far right lane of a three-lane highway during the day. There is an exit-only lane on the right, adjacent to the driver's lane. The driver is following a lead passenger vehicle closely. The passenger vehicle begins to slow in order to move to the left and into the middle lane. The CMV driver does not slow down appropriately and comes close to the rear of the passenger vehicle as it changes lanes.

TRAINING EXERCISE: After viewing the video, try to answer the following questions:

• Does the driver appear to adjust his vehicle's speed to maintain a safe following distance with the lead vehicle?
• Why was the lead vehicle slowing down?
• Why did the driver brake excessively?
• What could the driver have done differently?

TIP #2: Double Your Following Distance in Adverse Conditions

Adjust your following distance to appropriately match weather conditions, road conditions, visibility, and traffic. In emergency conditions, maintaining a safe distance from the vehicle in front of you will allow you to stop safely and/or to take necessary evasive action.78

Did You Know? The average stopping distance for a loaded tractor-trailer traveling at 55 mph (in ideal conditions) is 196 feet, compared with 133 feet for a passenger vehicle.79

Did You Know? Braking distance can be greatly affected by road surfaces, weather conditions such as rain, ice, and snow, or debris.78

KNOW THE DEFENSE

At 65 mph, a fully-loaded tractor-trailer requires a minimum of 665 feet of stopping distance. The most reliable method drivers use to gauge this distance is by counting seconds. To do this, pick a stationary object on the side of the road, like a road sign or overpass, and, as soon as the vehicle in front passes your chosen object, begin counting: “one-one-thousand, two-one-thousand…”. Continue counting until your vehicle reaches that stationary object.

In general, establishing a minimum following distance of six seconds is necessary. The chart below demonstrates.

At 65 mph, keeping one second of following distance means the vehicle is traveling 100 feet behind the vehicle in front. It takes an automobile a minimum of 150 feet to stop. With a 100 foot gap plus the auto’s stopping distance of 150 feet, an impact would occur within 250 feet. Since it takes a truck 665 feet to stop, it is clear that one second of following distance will result in a rear-end crash. It is not until six seconds of following distance is established that a tractor-trailer has sufficient stopping distance. These are in ideal conditions. Add one additional second for each hazard present, such as rain.

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This material is intended to be a broad overview of the subject matter and is provided for informational purposes only. Great West Casualty Company does not provide legal advice to its insureds, nor does it advise insureds on employment-related issues. Therefore, the subject matter is not intended to serve as legal or employment advice for any issue(s) that may arise in the operations of its insureds. Legal advice should always be sought from the insured’s legal counsel. Great West Casualty Company shall have neither liability nor responsibility to any person or entity with respect to any loss, action, or inaction alleged to be caused directly or indirectly as a result of the information contained herein.

Key Takeaways

Tailgating is the leading cause of rear-end collisions in the United States, causing more than 1,700 deaths and 500,000 injuries per year. In this guide for fleet managers, learn how to coach drivers to maintain a safe following distance. Plus, see how Samsara AI Dash Cams can detect and alert drivers to tailgating in real time, helping prevent accidents before they happen.

Following distance is the space between your vehicle and the vehicle in front of you while driving. It’s important for all drivers to maintain a safe following distance, so that they have time to safely stop in case the vehicle in front of them brakes abruptly. Since large commercial motor vehicles (CMVs) generally require more time to stop, it’s particularly important for CMV drivers to pay attention to their following distance.

How do you determine your following distance?

Following distance can be measured by the amount of time (in seconds) between you and the vehicle in front of you. You can measure your following distance by identifying a fixed object or stationary object on the side of the road, like a road sign, building, or tree. When the vehicle in front of you passes the stationary object, start counting “one thousand one, one thousand two…” in your head or out loud. Whatever number you are saying when your vehicle passes the stationary object determines your following distance. For example, if you are saying “one thousand four” when you pass the stationary object, then your following distance is roughly four seconds.

What is stopping distance?

Stopping distance is the distance it takes for your vehicle to come to a complete stop based on the current speed that you are traveling and your reaction time. Stopping distance is broken down into two components:

• Reaction distance: Reaction distance is the distance your vehicle travels from the time you see a reason to apply your brakes (like when you see brake lights in front of you) to when you actually begin to push the brake pedal down with your foot. Although this might seem like an insignificant amount of time, your vehicle can travel a significant distance in the time it takes you to react—especially at high speeds. For example, if you are driving 55 miles per hour (MPH) on a dry road surface, you are traveling approximately 81 feet per second. On average, it takes humans about 1.75 seconds from the time you see a reason to stop to when your brain tells you to take action. At 55 MPH, that translates to about 142 feet traveled in the time it takes you to react.

• Braking distance: Braking distance is the distance your vehicle travels from when its brakes are fully applied until it comes to a complete stop. Braking distance depends on many factors, including the speed you are traveling, the type of vehicle you’re driving, the condition of your brakes and tires, current road conditions, and more. Larger vehicles tend to be heavier and generally have a longer braking distance (meaning they require more time and space to stop). This is why many CMVs, like trucks and tractor trailers, have a longer stopping distance than cars.

Together, reaction distance and braking distance add up to your total stopping distance. To be driving at a safe following distance, the distance between your vehicle and the vehicle in front of you must be larger than your current stopping distance. This means you will have enough time and distance to safely stop in case the vehicle in front of you brakes abruptly.

What is a safe following distance for commercial motor vehicles?

A safe following distance is a distance that allows you enough time to safely come to a stop before colliding into the vehicle in front of you. There are many factors that can impact what a safe following distance is, depending on the type of vehicle you’re driving and the environment that you are in. Here are just a few of the factors that can affect the safe following distance in any given situation:

• Speed 

• Visibility and road conditions (including bad weather like snow, rain, or sleet)

• Vehicle type, weight, and length

• Tire and brake condition

• Reaction time

Maintaining a safe following distance is an important defensive driving technique for everyone—whether you’re operating a small passenger vehicle or a large truck. Because many CMVs require more time to come to a complete stop, it’s essential for professional drivers to pay close attention to their following distance at all times.

The FMCSA recommends that CMV drivers keep a following distance of one second for each 10 feet of vehicle length, with an additional second for speeds over 40 MPH. For example, for a 50-foot tractor trailer traveling at 55 MPH, the recommended following distance is at least 6 seconds. Here’s how it breaks down:

• The tractor trailer is 50 feet. One second per 10 feet of vehicle length = 5 seconds.

• The tractor trailer is traveling 55 MPH. One additional second for speeds over 40 MPH = 1 second.

• Total minimum following distance = 6 seconds.

The FMCSA also recommends drivers double their following distance when there are adverse driving conditions or inclement weather, such as rain, ice, snow, or debris. This is because bad weather conditions may cause your brakes to be less effective, increasing the stopping distance of your vehicle.

Why is tailgating so dangerous?

Tailgating is when a driver follows the vehicle ahead too closely (or maintains an unsafe following distance). Although tailgating is a common behavior that may seem harmless in the moment, it is actually quite dangerous. Tailgating can result in accidents, moving violations, fines, and lost revenue—as well as road rage incidents, serious accidents, injuries, and even fatalities. 

In fact, the NHTSA found that rear-end crashes are the most frequently occurring type of collision in the United States, accounting for approximately 29% of all crashes. Tailgating is the leading cause of these rear-end collisions, causing more than 1,700 deaths and 500,000 injuries per year. In addition to being a safety hazard, risky behaviors like tailgating can put a fleet out of business. A recent Frost & Sullivan report found that fatal accidents cost $10.8M on average.

Because many CMVs have a longer stopping distance than cars, it’s even more important for CMV drivers to avoid tailgating. According to the FMCSA, the average stopping distance for a loaded tractor-trailer traveling at 55 MPH (in ideal conditions) is 196 feet, compared with 133 feet for a passenger vehicle.

3 tips for coaching drivers on proper following distance

Tailgating can be a difficult behavior for fleet safety managers to coach drivers on, since you may not know it’s happening until it causes an accident. Here are a few safe driving tips and technology best practices to more effectively coach drivers about proper following distance and reduce tailgating across your fleet.

1. Debunk the three-second rule: The three-second rule is a popular way of thinking about following distance that is taught to many non-professional drivers in online driving courses or traffic safety schools when they are first getting their driver’s license from the DMV. The three-second rule states that you should simply leave three seconds-worth of room between you and the vehicle you are following. Although this rule (and others like it, such as leaving a certain number of car lengths-worth of space) can be helpful for non-professional drivers when they are first learning to drive, it’s not comprehensive enough for professional CMV drivers. A standard three-second following distance (or three-second gap) doesn’t take into account your vehicle’s speed, length, weight, road conditions, inclement weather, or other factors. In fact, the recommended proper following distance from the FMCSA is one second for each 10 feet of vehicle length, with an additional second for speeds over 40 MPH. Furthermore, the FMCSA recommends drivers double their following distance when there are adverse road conditions, including bad weather. Professional drivers should ensure they are always leaving enough space ahead of their vehicle, even when there is heavy traffic or they have a tailgater behind them. Following the FMCSA’s guidance (rather than the three-second rule) can help, but it can be difficult to calculate the necessary following distance in your head while driving. That’s where technology can help—keep reading to learn more.

2. Alert drivers when they are tailgating in real time: If you can alert drivers when they are tailgating in real time, they can immediately increase their following distance and avoid a potentially dangerous situation. Advanced artificial intelligence (AI) built into Samsara AI Dash Cams now makes this possible. Samsara AI Dash Cams can detect high-risk behaviors like tailgating and alert drivers to increase their following distance in the cab. Investing in this technology can pay off greatly by helping your fleet proactively prevent accidents before they happen.

3. Use real dash cam footage during coaching sessions: Coaching drivers with real footage of their own driving can be much more effective than using purchased safety training videos with actors. If you don’t already have dash cams, consider investing in a video-based safety solution that auto-uploads HD footage of risky behaviors, like tailgating and distracted driving. This makes it possible for your safety team to coach drivers in a timely manner based on real footage of their own behavior.

Coach drivers on tailgating and prevent accidents with Samsara AI Dash Cams

87% of all commercial motor vehicle crashes are the result of driver behavior or driver error, according to the NSTSCE. If your fleet has dealt with a tailgating accident in the past, you know how costly it can be to your business. 

Samsara AI Dash Cams enable fleets to coach drivers on following distance more effectively and consistently than ever before. Using advanced artificial intelligence (AI), Samsara AI Dash Cams can detect high-risk behavior (including tailgating and distracted driving) without a harsh event occurring. Combined with optional in-cab alerts, this makes it possible to minimize risky behavior and prevent accidents before they happen. With Samsara AI Dash Cams, you can:

• Alert drivers when they are tailgating in real time: Safety managers can also turn on optional in-cab alerts to warn drivers when they are tailgating at an unsafe speed, based on a minimum speed threshold that you can configure in your Samsara dashboard.

• Coach drivers on following distance with auto-uploaded HD footage: Using advanced artificial intelligence (AI), Samsara AI Dash Cams can automatically detect when drivers are following other vehicles too closely at high speeds and auto-upload these incidents to the dashboard for video-based coaching.

SeniorCare EMS—the largest commercial ambulance provider in New York City, with more than 1,300 employees—relies on Samsara AI Dash Cams to proactively prevent accidents before they happen by detecting risky driving behavior and providing in-cab audio alerts to drivers.

“It’s just amazing. We’re able to coach employees on the road,” said Safety Director Robert Ackerman. “We have seen many instances where the camera alerts the driver to distracted driving or tailgating, and they're able to avoid an accident.”

Reach out for a free trial to see how Samsara AI Dash Cams can protect your drivers, reduce accidents, and lower costs for your business.