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Dr. Christopher S. Baird

Why are truck drivers rude?

Category: Society      Published: August 26, 2013

Trucks have a lot of inertia and therefore take a lot longer than cars to safely slow down, speed up, or change lanes. Such slow responsivity can seem like rudeness to other drivers. Public Domain Image, source: OSHA.

Truck drivers are professional operators and are therefore less rude on the road in general than your typical driver. Truck drivers are often perceived to be rude for one simple reason: inertia.

Inertia (also called "momentum" or "Newton's First Law") means that an object in motion tends to stay in motion and resists change to its motion. Momentum is the product of two things: mass and speed. The higher the mass of an object, the more momentum it has, and the harder it is to stop or turn. Similarly, the faster an object is traveling, the more momentum it has and the harder it is to stop or turn. A bullet shot from a gun can do so much damage because it is traveling very fast despite being so light. Also, a road roller can do so much damage to your foot because it is very massive despite going very slowly. Large trucks are very massive compared to normals cars. Fully loaded, a semi-trailer truck has a mass 20 to 50 times that of a four-wheeled automobile. This fact means that it is 20 to 50 times harder to stop or turn a truck than a car simply because of its momentum. While a truck has a stronger engine, better brakes, and more wheels to help compensate for more inertia, these components are not magic. The bottom line is that a truck takes much longer to get up to speed and to slow down than a car because it is so massive. Also, trucks can not turn or change lanes as quickly as cars, as their high inertia would tip them over. It is simple physics at work and has nothing to do with driver attitudes or styles.

When a truck does not suddenly slow down to give your car room to merge onto a highway, it is not because the driver is rude. It is because the truck is so massive that it physically can not suddenly slow down. When a truck behind your car seems to be bearing down and you think he should back off, most likely you slowed down faster than the truck was able. His inertia carried him right onto your tail without the driver being able to do anything about it. If a truck seems to be going exceptionally slow around a sharp curve and is therefore in your way, realize that if he went faster he would likely tip over from his huge inertia. When changing lanes and expecting a truck to yield to you or make space for you, and he doesn't, he most likely can't. The heavier the load in the truck, the more inertia, and the more the truck has to drive like a lumbering beast. According to Report 400 of the National Cooperative Highway Research Program, cars require a minimum of between 450 and 900 feet in order to brake to a stop from a speed of 70 mph on a wet road. In contrast, trucks require a minimum of between 700 and 1400 feet to stop from the same speed under the same conditions. These spreads in values depend mostly on the state of the tires. Therefore, a truck with bad tires needs three times the distance of a car with good tires in order to screech to a stop from highway speed, even with the brakes completely engaged.

The best thing to do around trucks is to give them plenty of space, so they can safely turn, speed up, and slow down. Also, when merging to the same lane at the same time, the lighter vehicle should always yield to the more massive vehicle, as the more massive vehicle has more inertia and will have a harder time yielding.

Topics: conservation of momentum, inertia, laws of motion, momentum, semi trailer, truck