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Mechanics Corner: Anatomy of an accident

Brad Nelson Published on 11 September 2014

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If the word “accident” is used with something that has happened on the road or freeway, then some kind of crash or collision is generally part of the incident.

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Just for kicks, let’s dissect the events leading up to a recent crash/collision and see if the term “accident” really applies. For this discussion, I won’t even identify the location.

What happened was: A loaded hay truck, owned by the hay grower, collided with a piece of construction equipment parked in the lane of traffic that was blocked off due to re-paving.

The location was at the bottom end of 2 miles of a 5 percent downhill grade on a four-lane interstate highway. The base of this hill is posted for 50 miles per hour as the road makes a turn onto a bridge crossing a major river.

The result was: The machinery that was struck bounced off another piece of machinery, and the hay truck then struck two passenger vehicles, resulting in two non-life-threatening injuries. The rear trailer of the loaded hay truck overturned and scattered 3-by-4 hay bales at the crash site.

The freeway was closed for five hours, and by the time it was opened, it took another several hours to shoehorn the miles of backlogged traffic through the construction site.

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There are a number of possible causes for this incident. With rare exception, any time a motor vehicle strikes another vehicle or piece of machinery from the rear, the fault is with the vehicle that ran into or over something. The question is: Why?

Operator error in the form of inattention and driving too fast for conditions are usually the major factors in crashes. One of the most common operator errors is to descend a hill at a speed that requires heavy application of the service brakes in addition to the engine brake (or Jake brake) on the truck just to maintain control.

A truck (or any vehicle) should descend steep grades at a speed and with brake application so that an emergency stop while on the steep grade is possible.

Mechanical concerns that come into the picture start with brake adjustment. The brakes on passenger vehicles and light trucks (pickups) have had near-foolproof self-adjusters now for a couple of generations. That is not necessarily true for heavy trucks.

Trucks and trailers manufactured in the recent past come from the factory with both anti-lock brakes and automatic adjusters on the air brakes. Both of the current generation of these systems work fairly well most of the time but not well enough so that they can be ignored.

Still on the road are a number of trailers with neither of the above. The brakes on these must still be manually adjusted so that when the brakes are applied there is enough force there to quickly and evenly stop the vehicle. Even a 50-year-old trailer with manual slack adjusters, when properly adjusted, will have tremendous stopping power.

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When the adjustment is marginal, either due to inattention from the driver or truck shop, or because the automatic adjusters just “kind of” work, the stopping ability of the unit becomes marginal at most. Brakes gradually wear until they are out of adjustment. It can sneak up on a driver, which is why time spent under the truck and trailers checking and adjusting the brakes should be part of a pre-trip routine.

A pre-trip safety check should start with the part of the truck that contacts the road: the tires. Follow this with the brakes adjustment and function. For the lights, it’s more important to be seen than to see.

Brake and turn-signal lights must work and be visible. Note that the LED brake and turn-signal lights are much more visible than the older incandescent type. It helps your public relations if the headlights on your vehicles are properly aimed.

The simplest way to get it right is to make the adjustment on a foggy night. A properly adjusted headlight will light the road (on low-beam), while one out of adjustment (too high) will only glare back at the driver in the fog.

It’s a real plus if your drivers know how to use the dimmer switch on the headlights, too.

After an accident, expect your truck to be detained until the most aggressive truck safety inspectors on the face of the earth can be summoned to the scene. They will go over your truck with the fervor of crime scene investigators, which they are.

Any defect they find will be documented, and yes, it will be made available to the lawyers of the other party. Even if someone blows a stop sign in front of your vehicle and gets hit, you may be liable if your vehicle has defective brakes or lighting.

The post-accident inspection may also save your bacon.

For a modest sum of money starting south of $100, you can be the proud owner of your own digital video dash-camera. This creates a court-admissible record of what happened should your vehicle be involved in a crash. It may also alter the road manners of your drivers.

One fellow relayed the following: “The other driver wanted the officer investigating the wreck to start over with his statement on what happened when I asked him one question. That question was: ‘Would you like to revise your account of what happened before or after we play back the memory card from my dash-cam?’” PD

Brad Nelson is author of the column “Tales of a Hay Hauler.”

Photo courtesy of Brad Nelson.

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