CDL General Knowledge TestCombination Vehicles (if applicable)Hard
What is the primary danger of driving a combination vehicle with a bobtail tractor (no trailer) compared to driving a solo tractor or a full combination?
- AExcessive off-tracking in turns.
- BReduced traction on the drive wheels.
- CIncreased risk of jackknifing during braking.
- DSlower acceleration due to lighter weight.
Show answer & explanationAnswer & explanation
Correct answer: B. Reduced traction on the drive wheels.
When a tractor is bobtailing, there is no weight from the trailer on the fifth wheel to press down on the drive axles. This significantly reduces the traction of the drive wheels, making it easier to lose control, especially on slippery surfaces or during hard braking.
Why the other options are wrong
- A. Off-tracking is a characteristic of combination vehicles with trailers, not bobtail tractors.
- C. Jackknifing is more common with a trailer, not less when bobtailing.
- D. Lighter weight typically leads to faster, not slower, acceleration.
Bobtailing Hazards
Driving a tractor without a trailer (bobtailing) significantly reduces weight on the drive axles, leading to decreased traction and increased risk of losing control.
- Less weight on drive axles.
- Reduced traction.
- More prone to skidding/loss of control.
- Requires careful driving, especially in bad weather.
Memory trick: Light as a feather, slides like crazy.