Two Common Trucking Dangers: Driving Without A Trailer And Engine Braking

In our experience as truck accident lawyers, the two most common causes of serious or fatal truck accidents are driver fatigue and inadequate maintenance, which together are factors in more than half of all truck accidents nationwide. (That's why we support a new bill making GPS monitoring of truck drivers' hours mandatory.) But they’re not the only causes, and today I’d like to talk about two other common truck driving mistakes that we see.

Bobtailing is the colloquial term for driving a truck tractor without its trailer attached. At first glance, it would seem that a truck with tires and brakes designed to handle and to stop an 80,000-lbs trailer would perform even better without the trailer attached. In fact, a bobtailing truck is actually harder to drive and harder to stop, because it has a lot less traction on the rear wheels.

When the tractor has a trailer attached to it, the rear wheels of the tractor are supporting 10,000 pounds or more, which pushes the tires down onto the road. Without the trailer, all of the weight of the tractor (like from the engine and the cabin) is over the front two wheels, and there’s almost no weight at all on the rear wheels. Thus, if the truck driver encounters a sudden hazard and slams the brakes, the truck is going to behave like a bicycle when you use only the front brakes. The truck is going to tip forward, raising the rear wheels off the ground, which will both cause the truck to lose control and will make it take longer to stop, because friction is only being generated by the front two wheels and not all of the wheels.

Engine braking (aka Jake brakes) are another term for a compression release engine brake, a special part in truck engines that, when engaged, helps slow the truck by opening the exhaust valves in the engine cylinders, thereby slowing down the diesel engine cycle. Have you ever heard a truck suddenly make it sound like a machine gun? That’s the trucker using the Jake brake.

Using the Jake brake is useful in certain circumstances. For example, if a truck is just driving on the interstate and wants to slightly reduce speed without wearing down its brakes, the Jake brake is in effect pretty do that. Similarly, if a truck is in the mountains and driving down a very steep and long slope, using the Jake brake first can keep the regular desk and drum brakes available and cool for emergency stopping.

The problem comes in bad weather. Apart from a full lockup of the wheels, engine braking is usually more likely to cause skipping the normal braking. Thus, most truck manufacturers warn truck drivers not to use the exhaust brake in slippery conditions. Take this example from the Peterbilt manual:

WARNING! Do not use the exhaust brake when operating on surface with poor traction (such as wet, icy or snow covered roads). Retarders can cause the wheels to skid on a slippery surface. You could lose control of the vehicle and jackknife if the wheels begin to skid, resulting in an accident.

Now that you know the basics, think about this: what happens when a trucker uses engine braking while bobtailing?

For the answer, here’s another warning from the Peterbilt manual:

WARNING! Do not use an exhaust brake when driving bobtail or with an unloaded trailer. There may not be enough weight on the rear axle to provide traction. This could cause a lose of control and jackknife resulting in an injury accident. Make sure the exhaust brake is switched OFF when bobtailing or with an unloaded trailer.

So now you know: bobtailing and engine braking are a normal part of truck driving, but both carry unusual risks. Unfortunately, many inexperienced, poorly-trailed or overly fatigued truck drivers fail to recognize these risks, causing avoidable accidents.

Since 1958, The Beasley Firm has fought for the legal rights of injured persons, obtaining over $2 billion in jury awards and settlements. If you have been injured in a trucking accident, please feel free to contact our truck accident lawyers using this contact form or by calling 1.888.823.5291 for a free, confidential review.

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