The size, shape, weight, and configuration of a semi-tractor trailer combination, a.k.a. truck, semi, big rig, and 18-wheeler, inherently lend themselves to disaster when things go wrong.
A big rig consists of a tractor that is hooked onto a trailer at a pivot point that allows maneuverability, especially when backing. The trailer component of this pivot is known as the kingpin, which is secured to the tractor by means of a device called the fifth wheel. When this coupling system is not properly maintained, the ability of the vehicle to steer can be affected and lead to crashes. The tractor provides the power and direction to a passive trailer which carries freight. Up to three trailers can be pulled by a tractor, although each is shorter when pulled in combination.
The configuration of a tractor and trailer differs from that of a similar, but smaller class of vehicles known as straight truck, or box trucks. These vehicles require a class B license, (as opposed to a class A license for 18-wheelers,) and involve a rigid connection between the cargo-carrying portion of the truck and the tractor component.
Dimensions
Perhaps the most ominous characteristic of a truck is its massive weight. A commercial truck can legally weigh up to 80,000 pounds. Because of this extreme weight, equaling roughly 20 times that of an average passenger car, an impact created by a truck imparts massive destruction. Compared to the same collision pattern produced by a car of the same speed, a truck can crush several cars standing in its path and keep moving.
The weight of the truck must be distributed over the axles in such a fashion that no more than 12,000 pounds is exerted on the tractor’s front tires, with a maximum of 34,000 pounds on the tractor’s rear tires, and a maximum of 34,000 pounds on the trailer tires, which is the rearmost tire group on a big rig. The front of the trailer rests on the tractor’s rear tires, and contributes the vast majority of the weight falling on these tires.
The trailer can be up to 53 feet in length. Because of this, the rear tires do not exactly follow the path of the tractor’s tires, but rather lag to the inside of a curve when the vehicle turns. If a driver improperly sets up a turn, the rear of the trailer can run afoul of the road, crushing persons and property.
The maximum height of a truck is 13 feet six inches. This limit is reached by the trailer, not the tractor. If freight is loaded improperly, with a center of gravity that is either too high or lopsided, routine turns can lead to accidents since the width of a truck is only eight feet six inches, which is 63 percent of the height.
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Jackknife
The braking system in a truck is pneumatic. A compressor in the tractor is governed to maintain pressures between 100 and 125 pounds per square inch throughout the system. This pressurized air is transported through air hoses to storage tanks while waiting to be used, and travels through hoses to reach the braking devices attached to the axles.
An inherent characteristic of this system is that the air has a greater path to traverse in order to reach the brakes at the rear of the trailer than it does to reach the tractor’s brakes. While hydraulic fluid pressure travels through hoses in instant fashion, air pressure takes time to travel through air lines. Because of the time involved and the differential in distance, the trailer brakes then can engage up to a second or so after the tractor brakes.
If brakes are applied too abruptly, or if road conditions are slippery, this brief period during which the tractor is braking and therefore slowing itself, but the trailer is not, can create a situation in which the front of the trailer, (which is fixed to the tractor at the kingpin –fifth wheel coupling,) is being slowed by the tractor, but the rear of the trailer is still free to continue moving. Under circumstances of tire slippage, the rear of the trailer will therefore swing either to the right or left pursuant to Newton’s first law of motion, creating an increasingly folded configuration between the tractor and trailer. The relationship between tractor and trailer resembles a pocket jackknife and gives this type of accident its name. This bent configuration causes a loss of control of the vehicle as well as an invasion by the rear of the trailer into the adjacent lanes of traffic. Usually, the perpendicular relationship between the tractor and trailer involved in a jackknife prevents the entire unit from rolling over.
Tip Over
When the tractor and trailer remain in line, a rollover can occur when a truck takes a turn at excessive speeds, or while carrying freight that is loaded with a center of gravity that is either too high or off center. The relative extreme height of a trailer matched with a width of eight feet six inches, can leverage the centrifugal force of the trailer to the point at which it exceeds the centripetal force of the tires on pavement acting to keep the trailer moving along a curve. The top of the unit then tips over and the truck lands on its side causing massive damage to anything underneath.
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The FMCSA imposes numerous regulations on trucking companies, drivers, and the vehicles, themselves. Pursuant to an accident, violations of these regulations will not be evident on a standard police report. Some violations might be innocuous with regard to an accident whereas others might be culpable. If you or a loved one has suffered bodily injury or property damage as a result of a truck accident, you need the skill of an experienced accident attorney to determine which violations not only were committed, but also were causational factors in the accident. Assert your rights to receive compensation. Contact the car accident attorneys in Acworth, GAf at the Law Office of Roger Ghai, P.C. for a confidential consultation.
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