Gradient terminology: additional engine requirement The gradient on which an additional (banking/pusher) engine is required to assist trains in negotiating the ruling resistance is termed as:

Introduction / Context:
On steep sections, a single locomotive may not provide enough tractive effort to overcome grade resistance at required speeds. Railways classify gradients and define when helper (banking) locomotives are needed, which affects timetabling and locomotive assignment.

Given Data / Assumptions:

• We are identifying the terminology for a gradient requiring additional engine assistance.
• Trains otherwise meet load and traction norms on normal sections.

Concept / Approach:
A “pusher gradient” is a section where trains must be assisted by an additional engine—often attached at the rear (banker) or at the front—to negotiate the grade. This is distinct from “momentum gradient” (negotiated by run-up without sustained power increase) and “ruling gradient” (the most adverse gradient that governs load for the section).

Step-by-Step Solution:
Identify assistance requirement: need an additional locomotive.Match with terminology: pusher/banking gradient is the correct term.Differentiate from ruling gradient: ruling gradient governs load limits but may or may not need a banker depending on locomotive power.

Verification / Alternative check:
Operating manuals designate banker sections and instructions for attaching/detaching pushers; these are the pusher gradients.

Why Other Options Are Wrong:
Momentum gradient: Negotiated by speed carryover, not by attaching a helper.Ruling gradient: Governing gradient for load; not necessarily requiring a banker if power is adequate.Steep gradient: Descriptive but not the precise operating term.

Common Pitfalls:

• Equating any steep grade with pusher requirement without checking locomotive capability and tonnage profile.

Final Answer:
pusher gradient