For two-lane National Highways and State Highways in rural stretches, the standard roadway width (carriageway plus shoulders) is:

Introduction / Context:
Roadway width includes the carriageway and shoulders. For two-lane NH/SH in rural areas, adequate shoulders are required for breakdowns, non-motorized traffic refuge, and lateral clearance for safety and drainage.

Given Data / Assumptions:

• Two-lane undivided facility (one lane per direction).
• Rural/open terrain cross section with earthen or paved shoulders.

Concept / Approach:
Typical two-lane carriageway is about 7.0 m (two lanes of 3.5 m each). Adding shoulders commonly yields a roadway width of about 12 m (e.g., 2.5 m shoulders on each side), balancing safety and cost.

Step-by-Step Solution:
Carriageway ≈ 7.0 m.Add shoulders ≈ 2.5 m each side → 5.0 m total.Roadway width ≈ 7.0 + 5.0 = 12.0 m.

Verification / Alternative check:
Standard cross-section drawings for two-lane arterials in rural areas show 12 m roadway as a common adoption. Wider shoulders may be used depending on traffic mix and safety targets, but 12 m is widely referenced.

Why Other Options Are Wrong:

• 9–10.5 m and 9.5 m: insufficient shoulder width for safety and recovery on major corridors.
• 15 m: wider than typical baseline; used where generous shoulders/lanes are required.

Common Pitfalls:

• Confusing carriageway width (7.0 m) with roadway width.
• Underestimating shoulder needs in rural terrain with mixed traffic.

Final Answer:
12 m