Starting on a fairly steep ascending grade and curved territory, which action helps avoid string-line derailment?

Starting on a fairly steep ascending grade and curved territory, which action helps avoid string-line derailment?

• A. Use maximum throttle immediately
• B. Do not release brakes until fully stopped
• C. Maintain constant speed by using auto brake exclusively
• D. Allow brakes to fully release before starting and use only enough power to start

Answer: (D)

On a steep ascending grade with a curve, the key is to start moving in a balanced, controlled way so the cars don’t pull against each other and run off the rails along the curve. Releasing all brakes before starting eliminates the cross-car braking forces, and applying only enough power to just start the train keeps the initial motion smooth and evenly distributed. This avoids the heavy tug that can occur if brakes are still applied while you try to accelerate, which is what can trigger a string-line derailment on a curved grade. Keeping brakes on or delaying their release creates uneven forces across the train, or relies on automatic braking to hold a steady speed, which doesn’t respond quickly to the dynamic needs of starting on a curve. Maximizing throttle immediately without freeing the brakes also risks wheel slip and unbalanced traction, increasing derailment risk.

On a steep ascending grade with a curve, the key is to start moving in a balanced, controlled way so the cars don’t pull against each other and run off the rails along the curve. Releasing all brakes before starting eliminates the cross-car braking forces, and applying only enough power to just start the train keeps the initial motion smooth and evenly distributed. This avoids the heavy tug that can occur if brakes are still applied while you try to accelerate, which is what can trigger a string-line derailment on a curved grade.

Keeping brakes on or delaying their release creates uneven forces across the train, or relies on automatic braking to hold a steady speed, which doesn’t respond quickly to the dynamic needs of starting on a curve. Maximizing throttle immediately without freeing the brakes also risks wheel slip and unbalanced traction, increasing derailment risk.