According to the Nagpur Conference recommendations for early Indian highway planning, what should be the formation (roadway) width of an ideal National Highway constructed in hard rock cutting conditions?

Introduction / Context:
The Nagpur Conference (1943) laid the foundational guidelines for highway planning in India, including typical formation widths for different classes of roads and terrains. Hard rock cutting is a special case where excavation cost and constructability influence the recommended formation (roadway) width while still maintaining safety and operational requirements.

Given Data / Assumptions:

• Road class: National Highway (early Indian standards context).
• Terrain/condition: hard rock cutting.
• We seek the recommended formation width (overall roadway width on the formation).

Concept / Approach:
Historic Indian highway standards recognized that cutting through hard rock is costly and difficult. Consequently, recommended formation widths in such cuttings were slightly reduced relative to embankments or ordinary soil cuttings, without compromising traffic safety and drainage. Typical MCQ references from transportation engineering texts cite 7.5 m as the ideal formation width for National Highways in hard rock cutting under the Nagpur guidelines.

Step-by-Step Solution:
Identify the standard-setting source: Nagpur Conference recommendations.Recognize that hard rock cutting allows a narrower formation than embankment while retaining two-lane function.Select the quoted ideal value for NH in hard rock cutting: 7.5 m.

Verification / Alternative check:
Later Indian Roads Congress (IRC) practices evolved; however, exam questions referencing the Nagpur era typically expect 7.5 m for this specific case. This aligns with long-standing academic problem sets and handbooks used for competitive exams.

Why Other Options Are Wrong:

• 8.9 m and 7.9 m: larger than the commonly quoted Nagpur figure for hard rock cuttings.
• 6.9 m and 6.5 m: too narrow for the intended NH formation under classic recommendations.

Common Pitfalls:

• Confusing formation width with paved carriageway width (pavement plus shoulders vs. total formation).
• Mixing later IRC standards with historic Nagpur values; the question explicitly anchors to Nagpur recommendations.

Final Answer:
7.5 m