CDL Combination Vehicles TestDriving Combination Vehicles SafelyMedium
A commercial driver operating a combination vehicle notices that the trailer is constantly swaying even when driving on a straight, level road with no strong winds. What is the most likely cause of this persistent trailer sway?
- AThe glad hand connections between the tractor and trailer are leaking air.
- BThe tractor's kingpin is worn out, causing excessive play.
- CThe trailer's anti-lock braking system (ABS) is malfunctioning.
- DThe cargo in the trailer is improperly loaded, creating an unbalanced center of gravity.
Show answer & explanationAnswer & explanation
Correct answer: D. The cargo in the trailer is improperly loaded, creating an unbalanced center of gravity.
Persistent trailer sway, especially on straight roads without external factors like wind, is most commonly caused by an improperly loaded trailer. An unbalanced load shifts the center of gravity, making the trailer unstable and prone to swaying.
Why the other options are wrong
- A. Leaking glad hand connections would primarily affect the air brake system's performance, not directly cause persistent trailer sway.
- B. A worn kingpin could cause some play but is less likely to cause persistent, noticeable sway on a straight, level road compared to an unbalanced load.
- C. An ABS malfunction would affect braking, potentially causing wheel lock-up, but not ongoing sway during normal driving without braking.
Trailer Sway Causes
Trailer sway is the uncontrolled side-to-side movement of a trailer, often caused by improper loading, excessive speed, or strong winds.
- Unbalanced cargo is a major contributor to sway.
- Sway can lead to loss of control and jackknifing.
- Speed and road conditions also influence sway.
Memory trick: LOADS of sway can make you stray!