Hilly road location: The gradients adopted on trace cuts for hill roads are generally kept how, relative to the ruling gradient?

Introduction / Context:
During reconnaissance and preliminary location of hill roads, engineers cut narrow trace lines along hill slopes to test feasible alignments. The gradient along these traces must permit safe movement of survey teams, trial vehicles, and construction equipment while reflecting practical operational gradients.

Given Data / Assumptions:

• A ruling gradient is the desirable maximum gradient used for most of the route under normal conditions.
• Trace cuts are temporary alignments used for exploration and preliminary works.
• Safety and ease of movement are priorities during this stage.

Concept / Approach:

Since trace cuts precede final formation, they should not strain vehicles and equipment. Therefore, designers keep them easier (flatter) than the ruling gradient to allow for uncertainties, rough surfaces, and maneuvering space. A typical thumb rule is making them 10% to 20% flatter than the ruling value.

Step-by-Step Solution:

Verification / Alternative check:

Field practice references and manuals on hill road location consistently recommend easing trace cut gradients to account for temporary surfaces and limited traction.

Why Other Options Are Wrong:

• Equal to ruling gradient: leaves no buffer for temporary, rough conditions.
• 10%–20% steeper: unsafe and operationally difficult on provisional paths.
• None of these: incorrect because a standard easing margin is used.

Common Pitfalls:

• Mistaking trace-cut guidance for final formation gradient criteria.

Final Answer:

10% to 20% easier (flatter) than the ruling gradient.