CDL Combination Vehicles TestDriving Combination Vehicles SafelyMedium
A commercial driver is operating a combination vehicle on a two-lane road. The driver is approaching a curve and sees a 'Recommended Speed 35 MPH' sign. The vehicle's current speed is 50 MPH. What should the driver do?
- AApply the parking brake to slow down quickly before the curve.
- BReduce speed before entering the curve, then accelerate gradually through it.
- CMaintain current speed, as combination vehicles have a higher center of gravity and require momentum.
- DBegin braking immediately and steer into the curve at a reduced speed.
Show answer & explanationAnswer & explanation
Correct answer: B. Reduce speed before entering the curve, then accelerate gradually through it.
For combination vehicles, it's crucial to reduce speed to a safe level (often below the posted recommended speed for curves) before entering the curve. Braking in a curve can cause loss of control or a jackknife. Accelerating gradually through the curve helps maintain stability.
Why the other options are wrong
- A. Applying the parking brake while moving is extremely dangerous and will cause the drive wheels to lock up, leading to a skid or loss of control.
- C. Maintaining speed or relying on momentum is extremely dangerous in a curve for a combination vehicle due to rollover risk.
- D. Braking within a curve, especially with a combination vehicle, can lead to loss of traction, a skid, or a jackknife.
Safe Curve Negotiation
Reduce speed before entering a curve with a combination vehicle, then accelerate gradually through the curve to maintain stability.
- Braking in a curve increases rollover/jackknife risk.
- Enter curves slowly, accelerate gently out.
- Combination vehicles have higher rollover risk due to high center of gravity.
Memory trick: Curve ahead, slow your tread, accelerate through, don't be dead!