What defines a mountain grade in train handling?

A mountain grade in train handling is defined as having a slope of 2% or greater for a distance of 2 miles or more. This definition is important because it indicates a significant incline that requires careful handling of the train to maintain safety and efficiency. When trains operate on such grades, the forces acting on them are more pronounced, meaning that engineers must be prepared for challenges such as increased braking distances, potential for wheel slip, and the need for sufficient power to ascend or descend the grade.

The reasoning behind this standard is based on the need for operational awareness and proficiency in managing heavier loads and ensuring the train's stability. Train handling on steep grades demands specific techniques, including the appropriate use of dynamic brakes and air brakes, to maintain control.

In contrast, other definitions involving lower percentages or shorter distances do not meet the criteria that signify the special challenges posed by mountain grades, thus reinforcing the understanding that 2% for 2 miles or more is necessary for classifying a terrain as a mountain grade.