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Section 6: Combination Vehicles
This Section Covers:
- Driving Combinations
- Combination Vehicle Air Brakes
- Antilock Brake Systems
- Coupling and Uncoupling
- Inspecting Combinations
This section provides information needed to pass the tests for combination vehicles (tractor-trailer, doubles, triples, straight truck with trailer). The information is only to give you the minimum knowledge needed for driving common combination vehicles. You should also study Section 7 if you need to pass the test for doubles and triples.
6.1 – Driving Combination Vehicles Safely
Combination vehicles are usually heavier, longer, and require more driving skill than single commercial vehicles. This means that drivers of combination vehicles need more knowledge and skill than drivers of single vehicles. In this section, we talk about some important safety factors that apply specifically to combination vehicles.
6.1.1 – Rollover Risks
More than half of truck driver deaths in crashes result from truck rollovers. When more cargo is piled up in a truck, the "center of gravity" moves higher up from the road. The truck becomes easier to turn over. A fully loaded truck is ten times more likely to roll over in a crash than an empty truck.
To prevent a rollover, keep the cargo as close to the ground as possible, and drive slowly around turns. Keeping cargo low is even more important in combination vehicles than in straight trucks.
Also, keep the load centered on your truck, tractor, or semi. If the load is to one side so it makes a trailer lean, a rollover is more likely. Make sure your cargo is centered and spread out as much as possible. (Cargo distribution is covered in Section 3 of this manual.)
Rollovers happen when you turn too fast. Drive slowly around corners and when taking on-ramps and off-ramps. Avoid quick lane changes, especially when fully loaded.
Multiple-Choice Questions:
A fully loaded truck is how much more likely to roll over in a crash than an empty truck?
- 10 times
- 20 times
- About the same
- 2 times
More than half of truck driver deaths in crashes are the result of:
- Truck collisions
- Truck rollovers
- A truck running into the back of another truck
- Truck jackknifes
When more cargo is piled up in a truck:
- The "center of gravity" moves higher up from the road. The truck becomes easier to turn over.
- The "center of gravity" moves higher up from the road. The truck becomes harder to turn over.
- None of these are correct
- The "center of gravity" moves lower down near the road. The truck becomes harder to turn over.
To prevent a rollover:
- Keep the cargo as close to the ground as possible
- All these are correct
- Go slowly around turns
- Keep the load centered on your truck
To prevent a rollover, keep the cargo as close to the ground as possible, and drive slowly around turns. Keeping cargo low is even more important in combination vehicles than in straight trucks.
Also, keep the load centered on your truck, tractor, or semi. If the load is to one side so it makes a trailer lean, a rollover is more likely. Make sure your cargo is centered and spread out as much as possible. (Cargo distribution is covered in Section 3 of this manual.)
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