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How to Avoid Jackknifing


Anti-Jackknife Technology

Engineers have attacked the jackknifing problem from a few different angles. Some technologies involve adjusting the design of brakes, while others involve devices that physically prevent the trailer from veering too far.

Because brake locking can easily lead to jackknifing, the addition of anti-lock brakes on a tractor or a trailer (or both) is an effective countermeasure. Anti-lock brakes do just what the name implies: They prevent your wheels from locking up. They do this by equipping a vehicle with sensors that are on the lookout for unusual heavy braking. When you slam on your brakes and risk over-braking the wheels into a dangerous lock, this trips the sensor into decreasing the brake pressure on the wheel [source: AIADA].

By doing this, anti-lock brakes keep your wheel braking while preventing it from freezing into an all-out lock. Although you may not necessarily be able to brake faster with these, you will be able to control steering better by maintaining traction in avoiding skids [source: FMCSA]. While this is going on, you'll feel a pulsing in the brake pedal. You can learn more about this system and its different types in "How Anti-Lock Brakes Work." Studies indicate that anti-lock brakes have proven extremely beneficial for large rigs that are prone to jackknifing -- even though anti-lock brakes are no better than normal brakes in cars [source: Harris].

A similar kind of technology addresses the over-braking problems of empty trailers that we mentioned earlier. A load-sensing regulator reduces the brake pressure to the wheel when the load is light [source: Kawabe].

Besides adjusting brake systems, other types of anti-jackknifing technology usually have to do with preventing a tractor and its trailer from folding too far into each other. This is usually an addition to the coupling device that connects a tractor and trailer called the fifth wheel. The inherent difficulty with this type of anti-jackknife device is that a tractor-trailer needs to be able to bend dramatically when making sharp turns.

A few different technologies attempt to overcome this obstacle. For instance, one idea is a swing-limiting device on the fifth wheel that can be engaged and disengaged manually by the driver at the appropriate times [source: STS]. Other designers have developed a prevention device that limits the possible angle of swing once the vehicle reaches a certain threshold of speed and manually disengaged it later [source: Ball]. The logic here is that the device won't be engaged during sharp turns, which should be taken at low speeds.

As engineers perfect this technology (and truck drivers and towers become more aware of safe driving techniques), we can expect our roads to get safer.


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